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Objectives: The aims of this study were to (1) establish the maximum allowable interference limits for hemolysis, lipemia, and icterus for chemistry analytes tested in body fluid samples and (2) assess the effectiveness of serial dilution to mitigate spectral interferences., Methods: Residual body fluids from clinically ordered testing were mixed (<10% by volume) with stock solutions of interferent (spiked) and compared with a control spiked with an equal volume of 0.9% saline. The analytes were measured on the Roche cobas c501 instrument. Difference and percentage difference were calculated and compared with allowable total error limits. A subset of samples were serially diluted with 0.9% saline. Mean (SD) difference and percentage difference were calculated., Results: The interference thresholds were lower than the package insert for lactate dehydrogenase, cholesterol, triglycerides, and total protein for hemolysis; amylase, cholesterol, and total protein for icterus; and albumin for lipemia. Only cholesterol and triglyceride results returned to baseline upon dilution of icteric samples., Conclusions: Interference thresholds in body fluids were lower than blood for 6 analytes. Diluting interferences that surpass these limits does not produce reliable results that are comparable to the baseline results before spiking in the interferent., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Introduction: Multiple studies have investigated the role of cardiac troponin (cTn) in the risk stratification of patients with COVID-19. Most of these investigations are based on cTn values at presentation and do not consider the prognostic significance of cTn changes over time. This study aimed to investigate the prognostic role of serial cTn measurements in patients hospitalized with COVID-19 with samples that were not obtained for clinical indications., Methods: Patients hospitalized between April 2020 and March 2021 with PCR-confirmed SARS-CoV-2 infection were evaluated. Blood samples collected for any reason were stored for subsequent analysis. If clinical high sensitivity hs-cTnT (Roche) was not measured, samples were tested separately in batches. Hs-cTnI (Abbott) was also evaluated., Results: There were 228 unique patients. There were 21 (9.2 %) deaths. No patient with a low hs-cTnT (<6 ng/L) died and 1 patient with low hs-cTnI (<5 ng/L) died. Myocardial injury was associated with higher odds of death, when defined by hs-cTnT (OR: 7.88, 95 % CI: 2.04-30.40, p = 0.003) or hs-cTnI (OR: 7.46, 95 % CI: 2.68-20.77, p < 0.001). This association remained after propensity weighting. An increasing pattern was associated with higher odds of death compared to a stable pattern for hs-cTnT (OR: 5.45, 95 % CI: 1.81-16.40, p = 0.003) and hs-cTnI (OR: 4.49, 95 % CI: 1.02-19.81, p = 0.048). Among patients with myocardial injury defined by hs-cTnT, an increasing pattern was associated with higher odds of death compared to a decreasing pattern (OR: 4.80, 95 % CI: 1.16-19.97, p = 0.031)., Conclusions: Patients hospitalized with COVID-19 with myocardial injury have higher odds of death. Serial hs-cTn testing provides additional risk stratification in these patients., (Copyright © 2024 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: The accurate measurement of Low-density lipoprotein cholesterol (LDL-C) is critical in the decision to utilize the new lipid-lowering therapies like PCSK9-inhibitors (PCSK9i) for high-risk cardiovascular disease patients that do not achieve sufficiently low LDL-C on statin therapy., Objective: To improve the estimation of low LDL-C by developing a new equation that includes apolipoprotein B (apoB) as an independent variable, along with the standard lipid panel test results., Methods: Using β-quantification (BQ) as the reference method, which was performed on a large dyslipidemic population (N = 24,406), the following enhanced Sampson-NIH equation (eS LDL-C) was developed by least-square regression analysis: [Formula: see text] RESULTS: The eS LDL-C equation was the most accurate equation for a broad range of LDL-C values based on regression related parameters and the mean absolute difference (mg/dL) from the BQ reference method (eS LDL-C: 4.51, Sampson-NIH equation [S LDL-C]: 6.07; extended Martin equation [eM LDL-C]: 6.64; Friedewald equation [F LDL-C]: 8.3). It also had the best area-under-the-curve accuracy score by Regression Error Characteristic plots for LDL-C < 100 mg/dL (eS LDL-C: 0.953; S LDL-C: 0.920; eM LDL-C: 0.915; F LDL-C: 0.874) and was the best equation for categorizing patients as being below or above the 70 mg/dL LDL-C treatment threshold for adding new lipid-lowering drugs by kappa score analysis when compared to BQ LDL-C for TG < 800 mg/dL (eS LDL-C: 0.870 (0.853-0.887); S LDL-C:0.763 (0.749-0.776); eM LDL-C:0.706 (0.690-0.722); F LDL-C:0.687 (0.672-0.701). Approximately a third of patients with an F LDL-C < 70 mg/dL had falsely low test results, but about 80% were correctly reclassified as higher (≥ 70 mg/dL) by the eS LDL-C equation, making them potentially eligible for PCSK9i treatment. The M LDL-C and S LDL-C equations had less false low results below 70 mg/dL than the F LDL-C equation but reclassification by the eS LDL-C equation still also increased the net number of patients correctly classified., Conclusions: The use of the eS LDL-C equation as a confirmatory test improves the identification of high-risk cardiovascular disease patients, who could benefit from new lipid-lowering therapies but have falsely low LDL-C, as determined by the standard LDL-C equations used in current practice., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Background: Analytical sensitivity of 2 rapid antigen tests was evaluated for detection of presumed SARS-CoV-2 Omicron variants and earlier variants of concern., Methods: A total of 152 SARS-CoV-2 RNA positive samples (N and ORF1ab positive but S gene negative) were tested for SARS-CoV-2 antigen by ACON lateral flow and LumiraDx fluorescence immunoassays. Sensitivity within 3 viral load ranges was compared among these 152 samples and 194 similarly characterized samples collected prior to the circulation of the Delta variant (pre-Delta)., Results: Antigen was detected in >95% of pre-Delta and presumed Omicron samples for both tests at viral loads >500,000 copies/mL, and 65 to 85% of samples with 50,000-500,000 copies/mL. At viral load <50,000 copies/mL, antigen tests showed better sensitivity in detecting pre-Delta compared to Omicron variants. LumiraDx was more sensitive than ACON at low viral load., Conclusions: Antigen tests had decreased sensitivity for detecting presumed Omicron compared to pre-Delta variants at low viral load., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Introduction: In clinical practice, kidney (dys)function is monitored through creatinine-based estimations of glomerular filtration rate (eGFR: Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]). Creatinine is recognized as a late and insensitive biomarker of glomerular filtration rate (GFR). The novel biomarker proenkephalin (PENK) may overcome these limitations, but no PENK-based equation for eGFR is currently available. Therefore, we developed and validated a PENK-based equation to assess GFR., Methods: In this international multicenter study in 1354 stable and critically ill patients, GFR was measured (mGFR) through iohexol or iothalamate clearance. A generalized linear model with sigmoidal nonlinear transfer function was used for equation development in the block-randomized development set. Covariates were selected in a data-driven fashion. The novel equation was assessed for bias, precision (mean ± SD), and accuracy (eGFR percentage within ±30% of mGFR, P30) in the validation set and compared with MDRD and CKD-EPI., Results: Median mGFR was 61 [44-81] ml/min per 1.73 m 2 . In order of importance, PENK, creatinine, and age were included, and sex or race did not improve performance. The PENK-based equation mean ± SD bias of the mGFR was 0.5 ± 15 ml/min per 1.73 m 2 , significantly less compared with MDRD (8 ± 17, P  < 0.001) and 2009 CKD-EPI (5 ± 17, P  < 0.001), not reaching statistical significance compared with 2021 CKD-EPI (1.3 ± 16, P  = 0.06). The P30 accuracy of the PENK-based equation was 83%, significantly higher compared with MDRD (68%, P  < 0.001) and 2009 CKD-EPI (76%, P  < 0.001), similar to 2021 CKD-EPI (80%, P = 0.13)., Conclusion: Overall, the PENK-based equation to assess eGFR performed better than most creatinine-based equations without using sex or race., (© 2023 International Society of Nephrology. Published by Elsevier Inc.)

Rapid and widespread diagnostic testing is critical to providing timely patient care and reducing transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recently, the Visby Medical COVID-19 point of care (POC) test was granted emergency use authorization (EUA) for qualitative detection of SARS-CoV-2 nucleic acid at the point of care. We evaluated its performance characteristics using residual specimens (n = 100) collected from Mayo Clinic patients using nasopharyngeal (NP) swabs and placed in viral transport media (VTM). The same specimen was tested using both the laboratory reference method (RT-qPCR) and Visby test. The reference methods utilized included a laboratory developed test with EUA (Mayo Clinic Laboratories, Rochester, MN) using the TaqMan assay on a Roche Light Cycler 480 or a commercially available EUA platform (cobas® SARS-CoV-2; Roche Diagnostics, Indianapolis, IN). Positive, negative, and overall percent agreement between the Visby COVID-19 test and the reference method were calculated. Additionally, the limit of detection (LoD) claimed by the manufacturer (1112 copies/mL) was verified with serial dilutions of heat inactivated virus. The Visby COVID-19 test correctly identified 29/30 positive samples and 69/70 negative samples, resulting in an overall concordance of 98.0%, positive percent agreement of 96.7%, and negative percent agreement of 98.6%. The abbreviated LoD experiment showed that the analytical sensitivity of the method is as low as or lower than 500 copies/mL. Our study demonstrated that Visby COVID-19 is well-suited to address rapid SARS-CoV-2 testing needs. It has high concordance with central laboratory-based RT-qPCR methods, a low rate of invalid results, and superior analytical sensitivity to some other EUA POC devices., (Copyright © 2021. Published by Elsevier Inc.)

Introduction: The triglyceride (TG) threshold for diagnosis of chylous ascites in patients with portal hypertension remains uncertain., Methods: Retrospective analysis of lipoprotein electrophoresis was conducted in 286 consecutive ascites samples., Results: Ascitic TG ≥ 81 mg/dL is 95.4% sensitive and 94.6% specific for chylous ascites diagnosed by the presence of significant chylomicron population., Discussion: The cutoff for chylous ascites diagnosis should be TG ≥ 81 mg/dL., (Copyright © 2022 by The American College of Gastroenterology.)

Background: Among hypertensive patients, plasma renin activity is lower and the response to diuretic monotherapy greater in volume responsive hypertensive patients. We hypothesized that hormones influencing extracellular volume such as vasopressin / antidiuretic hormone (ADH) might permit the development of a simple test to identify those with volume-related hypertension. Such a test might be of particular benefit to the Black population which is purported to have a higher incidence of volume-related and responsive hypertension. Thus, using copeptin, a surrogate marker for ADH, we studied if there were differences in this hormone between those with and without volume responsive hypertension., Methods: Serum copeptin was measured in biobanked blood samples from the Genetic Epidemiology of Responses to Antihypertensives (GERA) I study and analyzed with other variables from the study dataset., Results: There was no relationship between PRA and copeptin values nor could the response in blood pressure be predicted by the copeptin values. However, baseline copeptin levels were higher in Black than in White subjects (7.5 pmol/L vs 5.4 pmol/L, P < 0.001) while plasma sodium and calculated plasma osmolality were slightly lower in keeping with the concept that Black subjects have more volume-related hypertension. In addition, after hydrochlorothiazide (HCTZ), copeptin was significantly lower in Black (6.2 pmol/L, P = 0.004) but unchanged in White subjects (5.2 pmol/L, P = 0.901) and there were also changes in sodium., Conclusion: The current study suggests differences in ADH physiology between hypertensive Black and White patients. However, the use of copeptin to identify volume responsive patients could not be confirmed., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ronstan Lobo, Leslie J Donato, LaTonya J Hickson, David O Hodge, Gary L Schwartz: None, Arlene Chapman: Dr. Chapman consults for Sanofi, Reata and Otsuka. John C Lieske: Dr. Lieske receives consulting fees from the American Board of Internal Medicine, Synlogic, Novobiome, Federation Bio, Cantero/ Bridgebio, Biomarin, Precision Biosciences, Intellia, Mirium, Alnylam, OxThera, Dicerna, Synlogoic, Orfan, and Novobiome, and grant support from Alnylam, Allena, Retrophin, OxThera, NIDDK, Synlogic, Novobiome, and Dicerna. Allan S Jaffe: Dr. Jaffe presently or in the past has consulted for most of the major diagnostic companies., (Copyright © 2022 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Direct current (DC) cardioversion is used to terminate cardiac arrhythmias. Current guidelines list cardioversion as a cause of myocardial injury., Objective: This study determined whether external DC cardioversion results in myocardial injury measured by serial changes in high-sensitivity cardiac troponin T (hs-cTnT) and high-sensitivity cardiac troponin I (hs-cTnI)., Methods: This was a prospective study of patients undergoing elective external DC cardioversion for atrial fibrillation. hs-cTnT and hs-cTnI were measured precardioversion and at least 6 hours postcardioversion. Myocardial injury was present when there were significant changes in both hs-cTnT and hs-cTnI., Results: Ninety-eight subjects were analyzed. Median cumulative energy delivered was 121.9 (interquartile range [IQR] 102.2-302.7) J. Multiple cases 23 (23.5%) required 300 J or more. Maximum cumulative energy delivered was 2455.1 J. There were small significant changes in both hs-cTnT (median precardioversion 12 [IQR 7-19) ng/L], median postcardioversion 13 [IQR 8-21] ng/L; P < .001) and hs-cTnI (median precardioversion 5 [IQR 3-10) ng/L], median postcardioversion 7 [IQR 3.6-11) ng/L; P < .001). Results were similar in patients with high-energy shocks and did not vary based on precardioversion values. Only 2 (2%) cases met criteria for myocardial injury., Conclusion: DC cardioversion resulted in a small but statistically significant changes in hs-cTnT and hs-cTnI in 2% of patients studied irrespective of shock energy. Patients with marked troponin elevations after elective cardioversion should be assessed for other causes of myocardial injury. It should not be assumed the myocardial injury was from the cardioversion., (© 2022 Heart Rhythm Society. Published by Elsevier Inc.)

New more effective lipid-lowering therapies have made it important to accurately determine Low-density lipoprotein-cholesterol (LDL-C) at both high and low levels. LDL-C was measured by the β-quantification reference method (BQ) (N = 40,346) and compared to Friedewald (F-LDL-C), Martin (M-LDL-C), extended Martin (eM-LDL-C) and Sampson (S-LDL-C) equations by regression analysis, error-grid analysis, and concordance with the BQ method for classification into different LDL-C treatment intervals. For triglycerides (TG) < 175 mg/dL, the four LDL-C equations yielded similarly accurate results, but for TG between 175 and 800 mg/dL, the S-LDL-C equation when compared to the BQ method had a lower mean absolute difference (mg/dL) (MAD = 10.66) than F-LDL-C (MAD = 13.09), M-LDL-C (MAD = 13.16) or eM-LDL-C (MAD = 12.70) equations. By error-grid analysis, the S-LDL-C equation for TG > 400 mg/dL not only had the least analytical errors but also the lowest frequency of clinically relevant errors at the low (<70 mg/dL) and high (>190 mg/dL) LDL-C cut-points (S-LDL-C: 13.5%, F-LDL-C: 23.0%, M-LDL-C: 20.5%) and eM-LDL-C: 20.0%) equations. The S-LDL-C equation also had the best overall concordance to the BQ reference method for classifying patients into different LDL-C treatment intervals. The S-LDL-C equation is both more analytically accurate than alternative equations and results in less clinically relevant errors at high and low LDL-C levels., Competing Interests: The authors declare no conflict of interest.

Background: Measurement of cholesterol within lipoprotein subfractions may aid in cardiovascular disease prediction. Simple, homogenous enzymatic assays for the direct measurement of lipoprotein subfractions have been developed to measure small dense low-density lipoprotein cholesterol (sdLDL-C), high-density lipoprotein-3 cholesterol (HDL3-C), and triglyceride-rich lipoprotein (TRL-C) cholesterol. The objective of this study was to determine biological variability for sdLDL-C, HDL3-C, and TRL-C in a healthy reference population to facilitate interpretation of these analytes., Methods: Serum samples were collected from 24 healthy subjects (n = 14 female/10 male) daily for 3 days while non-fasting, and daily for 5 days, weekly for 4 weeks, and monthly for 6 months after overnight fasting. sdLDL-C, HDL3-C, and TRL-C cholesterol were measured by homogenous enzymatic assays. Sources of variability (between-subject, within-subject, and analytical) were calculated using random-effects regression models. Reference change value (RCV) and index of individuality (II) for each time period were determined from the variance components., Results: Analytic variability (daily, weekly, and monthly CVA) was <3% for each analyte. Monthly within-subject variability (CVI) was 17.1% for sdLDL-C, 7.4% for HDL3-C, and 25.7% for TRL-C. Most of the monthly variation was attributed to between-subject variation for all 3 analytes. Overall RCVs for monthly measurements were 18.1 mg/dL for sdLDL-C, 6.1 mg/dL for HDL3-C, and 16.0 mg/dL for TRL-C. IIs were <0.6 for sdLDL-C and HDL3-C, and 0.81 for TRL-C., Conclusions: sdLDL-C, HDL3-C, and TRL-C showed moderate within-subject variability, but high between-subject variability, in a healthy reference population. Given the high individuality of each analyte, population-based reference intervals may be inadequate to detect clinically significant changes., Competing Interests: Authors’ Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest: Employment or Leadership: None declared. Consultant or Advisory Role: None declared. Stock Ownership: None declared. Honoraria: N.A. Baumann, Bio-Rad, AACC Annual Scientific Meeting and AACC regional meetings; D.R. Block, AACC Annual Scientific Meeting; travel and per-diem received by N.A. Baumann and D.R. Block for AACC Annual Scientific Meeting. Research Funding: None declared. Expert Testimony: None declared. Patents: None declared., (© American Association for Clinical Chemistry 2022. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Dysbetalipoproteinemia (hyperlipoproteinemia type III, HLP3) is a genetic disorder that results in the accumulation of cholesterol on highly atherogenic remnant particles. Traditionally, the diagnosis of HLP3 depended upon lipoprotein gel electrophoresis or density gradient ultracentrifugation. Because these two methods are not performed by most clinical laboratories, we describe here two new equations for estimating the cholesterol content of VLDL (VLDL-C), which can then be used for the diagnosis of HLP3. Using results from the beta-quantification (BQ) reference method on a large cohort of dyslipidemic patients (N = 24,713), we identified 115 patients with HLP3 based on having a VLDL-C to plasma TG ratio greater than 0.3 and plasma TG between 150 and 1,000 mg/dl. Next, we developed two new methods for identifying HLP3 and compared them to BQ and a previously described dual lipid apoB ratio method. The first method uses results from the standard lipid panel and the Sampson-NIH equation 1 for estimating VLDL-C ( S -VLDL-C), which is then divided by plasma TG to calculate the VLDL-C/TG ratio. The second method is similar, but the Sampson-NIH equation 1 is modified or enhanced ( eS -VLDL-C) by including apoB as an independent variable for predicting VLDL-C. At a cut-point of 0.194, the first method showed a modest ability for identifying HLP3 (sensitivity = 73.9%; specificity = 82.6%; and area under the curve (AUC) = 0.8685) but was comparable to the existing dual lipid apoB ratio method. The second method based on eS -VLDL-C showed much better sensitivity (96.5%) and specificity (94.5%) at a cut-point of 0.209. It also had an excellent AUC score of 0.9912 and was superior to the two other methods in test classification. In summary, we describe two new methods for the diagnosis of HLP3. The first one just utilizes the results of the standard lipid panel and the Sampson-NIH equation 1 for estimating (VLDL-C) ( S -VLDL-C) and can potentially be used as a screening test. The second method ( eS -VLDL-C), in which the Sampson-NIH equation 1 is modified to include apoB, is nearly as accurate as the BQ reference method. Because apoB is widely available at most clinical laboratories, the second method should improve both the accessibility and the accuracy of the HLP3 diagnosis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor RH declared a past co-authorship with the author ATR., (Copyright © 2022 Sampson, Wolska, Meeusen, Donato, Jaffe and Remaley.)

Background: Ceramides are bioactive lipid species that mediate numerous cell-signaling events. Elevated plasma ceramides concentration constitutes a risk factor for several pathologies. Multiple studies have affirmed the plasma concentrations of 4 specific ceramides (Cer16:0, Cer18:0, Cer24:0, and Cer24:1) can predict cardiovascular disease risk. Furthermore, these ceramides can be altered by many lipid-lowering therapies. Understanding the biological variability within an individual, and within a population, will further inform the clinical use of plasma ceramides as a biomarker. In this study, we aimed to define the intra- and interbiological variability of ceramides in a healthy reference population in a weekly and monthly manner., Methods: Fasting plasma from 24 healthy adults was collected daily (5 days), weekly (4 weeks), and monthly (7 months). Ceramide concentrations were measured with liquid chromatography-mass spectrometry (LC-MS). For analysis, we used random-effects regression models to estimate variance components., Results: The analytical variability was smaller compared to the biological variability overall. The greatest variation reported was between-subject variation for all ceramide species. The critical difference-reference change value (RCV) for within-subject variations monthly were 0.07 mcmol/L (Cer16:0), 0.04 mcmol/L (Cer18:0), 1.09 mcmol/L (Cer24:0), and 0.27 mcmol/L (Cer24:1). The index of individuality (IOI) of ceramides were 0.82 (Cer16:0), 0.96 (Cer18:0), 1.06 (Cer24:0), and 0.89 (Cer24:1). The most consistent ceramide species was Cer18:0 with the lowest within- and between-subject critical differences in weekly and monthly measurements., Conclusions: Overall, this study demonstrates that the variability of ceramide concentrations at different time points is minimal within individuals, allowing a single draw to be sufficient at least in a yearly time frame., (© American Association for Clinical Chemistry 2022. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Increased fecal bile acid excretion (IBAX) occurs in a third of patients with functional diarrhea., Aims: To assess the prevalence of IBAX in benign inflammatory intestinal and colonic diseases presenting with chronic diarrhea., Methods: All patients with known inflammatory diseases or resections who underwent 48 h fecal fat and BA testing for chronic diarrhea at a single center were included. Quiescent disease was based on clinical evaluation and serum, endoscopic and imaging studies. IBAX was defined by: > 2337 µmol total BA/48 h; or primary fecal BAs > 10%; or > 4% primary BA plus > 1000 µmol total BA /48 h. Demographics, fecal weight, fecal fat, stool frequency and consistency were collected. Nonparametric statistical analyses were used for group comparisons., Results: Sixty patients had celiac disease (51 quiescent, 9 active), 66 microscopic colitis (MC: 34 collagenous, 32 lymphocytic), 18 ulcerative colitis (UC), and 47 Crohn's disease (CD). Overall, fecal fat, 48 h stool weight, frequency and consistency were not different among subgroups except for inflammatory bowel disease (IBD) based on disease location. Almost 50% patients with celiac disease and MC had IBAX, with a greater proportion with increased primary fecal BA. Among UC patients, rates of IBAX were higher with pancolonic disease. A high proportion of patients with ileal resection or CD affecting ileum or colon had IBAX. IBAX was present even with quiescent inflammation in UC or CD., Conclusions: A significant subset of patients with MC, quiescent celiac disease and IBD had increased fecal BA excretion, a potential additional therapeutic target for persistent diarrhea., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background Accurate measurement of the cholesterol within lipoprotein(a) (Lp[a]-C) and its contribution to low-density lipoprotein cholesterol (LDL-C) has important implications for risk assessment, diagnosis, and treatment of atherosclerotic cardiovascular disease, as well as in familial hypercholesterolemia. A method for estimating Lp(a)-C from particle number using fixed conversion factors has been proposed (Lp[a]-C from particle number divided by 2.4 for Lp(a) mass, multiplied by 30% for Lp[a]-C). The accuracy of this method, which theoretically can isolate "Lp(a)-free LDL-C," has not been validated. Methods and Results In 177 875 patients from the VLDbL (Very Large Database of Lipids), we compared estimated Lp(a)-C and Lp(a)-free LDL-C with measured values and quantified absolute and percent error. We compared findings with an analogous data set from the Mayo Clinic Laboratory. Error in estimated Lp(a)-C and Lp(a)-free LDL-C increased with higher Lp(a)-C values. Median error for estimated Lp(a)-C <10 mg/dL was -1.9 mg/dL (interquartile range, -4.0 to 0.2); this error increased linearly, overestimating by +30.8 mg/dL (interquartile range, 26.1-36.5) for estimated Lp(a)-C ≥50 mg/dL. This error relationship persisted after stratification by overall high-density lipoprotein cholesterol and high-density lipoprotein cholesterol subtypes. Similar findings were observed in the Mayo cohort. Absolute error for Lp(a)-free LDL-C was +2.4 (interquartile range, -0.6 to 5.3) for Lp(a)-C<10 mg/dL and -31.8 (interquartile range, -37.8 to -26.5) mg/dL for Lp(a)-C≥50 mg/dL. Conclusions Lp(a)-C estimations using fixed conversion factors overestimated Lp(a)-C and subsequently underestimated Lp(a)-free LDL-C, especially at clinically relevant Lp(a) values. Application of inaccurate Lp(a)-C estimations to correct LDL-C may lead to undertreatment of high-risk patients.

Background: Dyslipoproteinemias can be classified by their distinct lipoprotein patterns, which helps determine atherosclerotic cardiovascular disease (ASCVD) risk and directs lipid management but this has required advanced laboratory testing., Objective: To develop a new algorithm for classifying lipoprotein disorders that only relies on the standard lipid panel., Methods: Lipid thresholds for defining the different lipoprotein phenotypes were derived for Non-High-Density Lipoprotein-Cholesterol (NonHDL-C) and Triglycerides (TG) to be concordant when possible with the current US Multi-Society guidelines for blood cholesterol management., Results: The new classification method categorizes patients into all the classical Fredrickson-like phenotypes except for Type III dysbetalipoproteinemia. In addition, a new hypolipidemic phenotype (Type VI) due to genetic mutations in apoB-metabolism is described. The validity of the new algorithm was confirmed by lipid analysis by NMR (N = 11,365) and by concordance with classification by agarose gel electrophoresis/beta-quantification (N = 5504). Furthermore, based on the Atherosclerosis Risk in Communities (ARIC) cohort (N = 14,742), the lipoprotein phenotypes differ in their association with ASCVD (TypeV>IIb > IVb > IIa > IVa > normolipidemic) and can be used prognostically as risk enhancer conditions in the management of patients., Conclusions: We describe a clinically useful lipoprotein phenotyping system that is only dependent upon the standard lipid panel. It, therefore, can be easily implemented for increasing compliance with current guidelines and for improving the care of patients at risk for ASCVD., (© 2021. The Author(s).)

Objectives: To evaluate the analytical and clinical performance characteristics of the fifth-generation troponin T reagent., Methods: Troponin T was measured in 2,332 paired serum and plasma samples from emergency department and hospital patients using the fourth- and fifth-generation reagents. Testing was repeated after recentrifugation to determine the frequency of analytical outliers and percentage of patients with elevated values for each assay. We conducted separate experiments to determine the effects of biotin and hemolysis interference, as well as measure interinstrument variability, for fifth-generation troponin T., Results: Analytic outliers occurred more frequently using the fifth-generation reagent (3.4%) compared with the fourth-generation reagent (1.0%). The frequency of elevated troponin T above the 99th percentile upper reference limit was 26% for the fourth-generation reagent and 52% for the fifth-generation reagent. Clinically significant assay interference by biotin was observed at 20 ng/mL, but hemolysis interference was not observed until an H index of 150. Instrument-to-instrument variability between e411 and e601/602 instrument platforms is predicted to confound clinical interpretation of troponin changes., Conclusions: Analytical outliers and instrument-to-instrument variability are the two analytical variables most likely to confound interpretation of changes in fifth-generation troponin T results over time., (© American Society for Clinical Pathology, 2021. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: We evaluated the analytical sensitivity and specificity of 4 rapid antigen diagnostic tests (Ag RDTs) for severe acute respiratory syndrome coronavirus 2, using reverse transcription quantitative PCR (RT-qPCR) as the reference method and further characterizing samples using droplet digital quantitative PCR (ddPCR) and a mass spectrometric antigen test., Methods: Three hundred fifty (150 negative and 200 RT-qPCR positive) residual PBS samples were tested for antigen using the BD Veritor lateral flow (LF), ACON LF, ACON fluorescence immunoassay (FIA), and LumiraDx FIA. ddPCR was performed on RT-qPCR-positive samples to quantitate the viral load in copies/mL applied to each Ag RDT. Mass spectrometric antigen testing was performed on PBS samples to obtain a set of RT-qPCR-positive, antigen-positive samples for further analysis., Results: All Ag RDTs had nearly 100% specificity compared to RT-qPCR. Overall analytical sensitivity varied from 66.5% to 88.3%. All methods detected antigen in samples with viral load >1 500 000 copies/mL RNA, and detected ≥75% of samples with viral load of 500 000 to 1 500 000 copies/mL. The BD Veritor LF detected only 25% of samples with viral load between 50 000 to 500 000 copies/mL, compared to 75% for the ACON LF device and >80% for LumiraDx and ACON FIA. The ACON FIA detected significantly more samples with viral load <50 000 copies/mL compared to the BD Veritor. Among samples with detectable antigen and viral load <50 000 copies/mL, sensitivity of the Ag RDT varied between 13.0% (BD Veritor) and 78.3% (ACON FIA)., Conclusions: Ag RDTs differ significantly in analytical sensitivity, particularly at viral load <500 000 copies/mL., (© American Association for Clinical Chemistry 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Serologic testing for SARS-CoV-2 can be used for evaluation of past infection in individual patients and for community seroprevalence studies. We evaluated the analytical and clinical performance of the Genalyte Maverick SARS-CoV-2 Multi-Antigen Serology Panel compared to the Roche Elecsys Anti-SARS-CoV-2 nucleocapsid (NC) qualitative immunoassay, using well characterized clinical serum samples. A total of 143 pre-pandemic sera and 48 sera collected from patients with a negative molecular SARS-CoV-2 result were used for specificity studies. For sensitivity analyses, 179 sera were used, obtained 3-7 days, 8-14 days, or ≥ 15 days after symptom onset from patients with confirmed SARS-CoV-2 infection. Specificity was determined to be 95.3% (182/191) for the Genalyte Maverick. Overall sensitivity of the Genalyte Maverick was similar to that observed for the Roche Elecsys NC test, 79.3% (142/179) vs. 76.5% (137/179), respectively. Genalyte Maverick trended, without statistical significance, towards higher sensitivity as compared to the Roche Elecsys NC test in the 3-7 days (11/25 vs. 9/25, respectively) and 8-14 days (21/28 vs. 19/28, respectively) post-symptom onset sample sets, but was identical in the ≥ 15 days post-symptom onset group (106/116 vs. 106/116, respectively). Therefore, the Genalyte Maverick serologic test had similar overall sensitivity to the Roche Elecsys NC assay, but may have slightly improved sensitivity for early seroconversion. The lower Genalyte Maverick specificity as compared to the Roche Elecsys NC assay as reported by other studies (>99%), may necessitate confirmatory testing of positive Genalyte Maverick results if implemented for clinical use., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Authors. Published by Elsevier Ltd.)

Objective: To identify the diagnoses and outcomes associated with elevated high sensitivity cardiac troponin T (hs-cTnT) compared with the 4th-generation troponin T and to validate the Mayo Clinic hs-cTnT myocardial infarction algorithm cutoff values., Patients and Methods: Consecutive blood samples of patients presenting to the emergency department between July 2017 and August 2017, who had 4th-generation troponin T, were also analyzed using the hs-cTnT assay. Troponin T values, discharge diagnoses, comorbidities, and outcomes were assessed. In addition, analyses of sex-specific and hs-cTnT cutoff values were assessed., Results: Of 830 patients, 32% had an elevated 4th-generation troponin T, whereas 64% had elevated hs-cTnT. With serial sampling, 4th-generation troponin missed a chronic myocardial injury pattern and acute myocardial injury pattern in 64% and 16% of patients identified with hs-cTnT, respectively. Many of these "missed" patients had discharge diagnoses associated with cardiovascular disease, infection, or were postoperative. Five of the 6 patients with unstable angina ruled in for myocardial infarction., Conclusion: There were many increases in hs-cTnT that were missed by the 4th-generation cTnT assay. Most new increases are not related to acute cardiac causes. They were more consistent with chronic myocardial injury. High-sensitivity cTnT did reclassify most patients with unstable angina as having non-ST-elevation myocardial infarction. Older age, more comorbidities, and lower hemoglobin were associated with elevated hs-cTnT. Our data also support the use of our sex-specific cutoff values., (Copyright © 2021. Published by Elsevier Inc.)

Background: It is important for clinical laboratories to have protocols for investigating suspected biotin interference in patient samples. VeraPrep Biotin™ is a commercial product used to rapidly deplete biotin from serum/plasma samples. The objectives of this study were to verify that VeraPrep Biotin™: (a) does not impact immunoassay analyte recovery in control samples and (b) can effectively deplete biotin from samples (both biotin-spiked and samples from donors who ingested biotin supplements)., Methods: De-identified residual waste serum/plasma samples were combined to create 9 pools for each immunoassay. Plasma/serum samples (n = 23) were obtained from 6 healthy donors at varying times following ingestion of biotin (20 mg, 100 mg, or 200 mg). Nine Elecsys immunoassays were evaluated using the e 602 (Roche Diagnostics Inc.). Control, biotin-spiked (n = 10, ∼400 ng/mL), and donor samples were assayed pre- and post-VeraPrep treatment. Percentage analyte recovery [(posttreatment/pretreatment) × 100] was calculated for control samples. A laboratory-developed LC-MS/MS method was used to quantify biotin., Results: In control samples (n = 81), 90-110% analyte recovery was observed post-VeraPrep treatment in over 95% of samples (77/81). The pre- and post-VeraPrep treatment biotin concentration [mean ± standard deviation (SD)] for specimens spiked with up to 500 ng/mL biotin was 357 ± 47 ng/mL and 1.0 ± 0.6 ng/mL, respectively. The mean (range) biotin concentration for the donor samples pre- and post-treatment was 166 (15-1029)  ng/mL and 0.2 (<0.1-3)  ng/mL, respectively (P = 0.004)., Conclusions: These data demonstrate that treatment with VeraPrep Biotin™ does not affect analyte recovery in biotin-negative samples and effectively depletes both spiked and endogenous biotin in serum/plasma., (© American Association for Clinical Chemistry 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objectives: Excessive fecal bile acids in adults have been associated with diarrhea-predominant irritable bowel syndrome (IBS-D), but their role in pediatric IBS-D is unknown. Serum markers including 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor-19 (FGF-19) were validated in adults to detect bile acid diarrhea (BAD) compared to 48-hour fecal bile acid collection (48FBA). Our aims were to assess fasting serum C4 and FGF-19 and 48FBA in a pediatric population, to compare measurements in IBS-D patients and healthy controls (HC), and to determine the prevalence of BAD among children with IBS-D., Methods: Using a cross-sectional design, 26 patients with IBS-D and 56 HC were recruited in two pediatric tertiary care centers. Fasting serum C4 and FGF-19 and 48FBA were obtained. Participants completed a 7-day bowel diary coinciding with stool collection. Associations were analyzed using Spearman correlations., Results: Mean age was 14.7 ± 2.5 years (42.3% female) in IBS-D and 12.6 ± 2.4 years (39.3% female) in HC. There was a significant correlation of C4 with 48FBA (r = 0.48, P < 0.05) and an inverse association with FGF-19 (r = -0.43, P < 0.05). No significant differences were noted in C4 (P = 0.32), FGF-19 (P = 0.1), or 48FBA (P = 0.5) between IBS-D and HC groups; however, 20% of IBS-D patients had elevated C4 and 28% had low FGF-19 values.Fecal primary BA was significantly correlated with stool frequency (r = 0.45, P < 0.002)., Conclusions: Correlations of C4 with 48FBA and FGF-19 are confirmed in a pediatric population. Twenty percent of pediatric patients with IBS-D had abnormal fasting serum C4. This serum test could be applied to identify BAD in pediatric IBS-D., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.)

Point-of-care (POC) tests are in high demand in order to facilitate rapid care decisions for patients suspected of SARS-CoV-2. We conducted a clinical validation study of the Cue Health POC nucleic acid amplification test (NAAT) using the Cue lower nasal swab, compared to a reference NAAT using standard nasopharyngeal swab, in 292 symptomatic and asymptomatic outpatients for SARS-CoV-2 detection in a community drive through collection setting. Positive percent agreement between Cue COVID-19 and reference SARS-CoV-2 test was 91.7% (22 of 24); or 95.7% (22 of 23) when one patient with no tie-breaker method was excluded. Negative percent agreement was 98.4% (239 of 243), and there were 25 (8.6%) invalid or canceled results. The Cue COVID-19 test demonstrated very good positive and negative percent agreement with central laboratory tests and will be useful in settings where accurate POC testing is needed to facilitate management of patients suspected of COVID-19., (Copyright © 2021 Elsevier Inc. All rights reserved.)

[Figure: see text].

Background: Severe hypertriglyceridemia (HTG) is a common cause of acute pancreatitis, although even moderate HTG may elevate this risk. Identifying patients who are prone to hypertriglyceridemic pancreatitis (HTGP) can facilitate early, preventative interventions., Objective: To examine advanced lipoprotein profile (ALP) of hypertriglyceridemic patients with and without HTGP to identify lipid and lipoprotein parameters which may help improve risk stratification., Methods: This was a retrospective cohort study of adult patients with serum triglycerides (TGs) ≥ 500 mg/dL who underwent ALP testing. Chart reviews were conducted to identify those who developed HTGP or not. Comparisons of lipid profiles of patients with and without HTGP were performed using chi-square or rank-sum tests. ROC curves were generated to identify lipid and lipoprotein parameters which helped improve prediction of HTGP beyond serum TG levels., Results: Fifty-eight subjects were included in the analysis. Twenty had at least one documented episode of HTGP. Among patients with HTGP, median serum TG concentrations were 2832 mg/dL vs. 978 mg/dL in the non-pancreatitis group (p < 0.001). Chylomicron TG/total TG, chylomicron TG/VLDL TG, chylomicron TG/apoB, total TG/total Cholesterol, and total TG/apoB were significantly higher among the pancreatitis group. Total serum TG/apoB had the best discriminant value for predicting HTGP with an AUC-ROC of 0.87 (p < 0.001). A cutoff of >10.6 was associated with a sensitivity of 90% and specificity of 75%., Conclusion: Measurement of serum apoB levels and calculation of serum TG/apoB ratio may help identify hypertriglyceridemic patients at risk for HTGP., (Copyright © 2020 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Ceramides are bioactive lipids that act as secondary messengers for both intra- and inter-cellular signaling. Elevated plasma concentrations of ceramides are associated with multiple risk factors of atherosclerotic cardiovascular diseases and comorbidities including obesity, insulin resistance and diabetes mellitus. Furthermore, atherosclerotic plaques have been shown to be highly enriched with ceramides. Increases in ceramide content may accelerate atherosclerosis development by promoting LDL infiltration to the endothelium and aggregation within the intima of artery walls. Thus, ceramides appear to play a key role in the development of cardiometabolic disease due to their central location in major metabolic pathways that intersect lipid and glucose metabolism. Recently published data have shown that ceramides are not only of scientific interest but may also have diagnostic value. Their independent prognostic value for future cardiovascular outcomes over and above LDL cholesterol and other traditional risk factors have consistently been shown in numerous clinical studies. Thus, ceramide testing with a mass spectrometer offers a simple, reproducible and cost-effective blood test for risk stratification in atherosclerotic cardiovascular diseases., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Lipoprotein(a) [Lp(a)] is a pro-atherogenic and pro-thrombotic LDL-like particle recognized as an independent risk factor for cardiovascular disease (CVD). The cholesterol within Lp(a) (Lp(a)-C) contributes to the reported LDL-cholesterol (LDL-C) concentration by nearly all available methods. Accurate LDL-C measurements are critical for identification of genetic dyslipidemias such as familial hypercholesterolemia (FH). FH diagnostic criteria, such as the Dutch Lipid Clinic Network (DLCN) criteria, utilize LDL-C concentration cut-offs to assess the likelihood of FH. Therefore, failure to adjust for Lp(a)-C can impact accurate FH diagnosis and classification, appropriate follow-up testing and treatments, and interpretation of cholesterol-lowering treatment efficacy., Objective: In this study, we use direct Lp(a)-C measurements to assess the potential misclassification of FH from contributions of Lp(a)-C to reported LDL-C in patient samples submitted for advanced lipoprotein profiling., Methods: A total of 31,215 samples submitted for lipoprotein profiling were included. LDL-C was measured by beta quantification or calculated by one of three equations. Lp(a)-C was measured by quantitative lipoprotein electrophoresis. DLCN LDL-C cut-offs were applied to LDL-C results before and after accounting for Lp(a)-C contribution., Results: Lp(a)-C was detected in 8665 (28%) samples. A total of 940 subjects were reclassified to a lower DLCN LDL-C categories; this represents 3% of the total patient series or 11% of subjects with measurable Lp(a)-C., Conclusion: Lp(a)-C is present in a significant portion of samples submitted for advanced lipid testing and could cause patient misclassification when using FH diagnostic criteria. These misclassifications could trigger inappropriate follow-up, treatment, and cascade testing for suspected FH., (Copyright © 2020 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Approximately one-third of patients with IBS-diarrhea (IBS-D) have increased bile acid (BA) synthesis or excretion. An open-label study showed benefits of colesevelam on bowel functions, consistent with luminal BA sequestration by colesevelam. We compared the effects of colesevelam vs placebo on symptoms and gene expression patterns in the sigmoid colon mucosa in patients with BA diarrhea associated with IBS-D., Methods: We performed a double-blind, parallel-group study of 30 adults with IBS-D and evidence of increased BA synthesis or fecal excretion, from December 2017 through December 2018 at a single center. Patients were randomly assigned (1:1) to groups given colesevelam (3 tablets, 625 mg each) or matching placebo, orally twice daily for 4 weeks. Stool diaries documented bowel functions for 8 days before and 28 days during colesevelam or placebo. Stool and fasting serum samples were collected for analyses of fecal BAs and serum levels of C4 and FGF19. We measured colonic transit by scintigraphy, mucosal permeability by in vivo excretion of saccharide probes, and mRNA levels in rectosigmoid biopsies. All measurements were made at baseline and on the last days of treatment. The primary endpoints were change in total fecal BA concentration and stool consistency., Results: Compared with placebo, colesevelam was associated with significant changes in sequestered fecal total BA excretion (P < .001) and serum levels of C4 and FGF19 (both P < .001), and with a mean increase in fecal level of deoxycholic acid (10%; P = .07) compared to placebo. Colesevelam decreased colon mucosal expression of NR1H4 and P2RY4 and increased expression of GPBAR1, compared with baseline. Stool frequency and consistency, colonic transit, and permeability did not differ significantly between groups. Colesevelam was well tolerated., Conclusions: In a randomized trial, we found that colesevelam increases delivery of total and secondary BAs to stool, hepatic BA synthesis, and colonic mucosal expression of genes that regulate BA, farnesoid X, and GPBAR1 receptors. Larger studies are needed to determine the effects on clinical responses. ClinicalTrials.gov no: NCT03270085., (Copyright © 2020 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Ceramides are bioactive lipids that have an important role in many cellular functions such as apoptosis and inflammation. During the past decade emerging clinical data have shown that ceramides are not only of great biochemical interest but may also have diagnostic utility. Ceramides have shown independent predictive value for negative cardiovascular outcomes as well as for the onset of type 2 diabetes. Based on abundant published data, risk score using the concentrations of circulating ceramides have been developed and adapted for routine clinical practice. Currently serum ceramides are used clinically as efficient risk stratifiers for primary and secondary prevention of atherosclerotic cardiovascular disease (CVD). A direct cause-effect relationship between CVD and ceramide has not been established to date. As ceramide-specific medications are being developed, conventional strategies such as lipid lowering agents and lifestyle interventions can be used to reduce overall risk. Ceramides can identify a very high-risk coronary heart disease category of patients in need for more intense medical attention, specifically those patients at higher risk as highlighted in the 2019 European Society of Cardiology guidelines for stable chronic coronary syndrome patients. In addition, the ceramide risk score may be used as a decision-making tool in primary prevention patients with moderate CVD risk. Finally, the ceramide risk score may have a unique utility as a motivational tool to increase patient's adherence to medical therapy and lifestyle changes., (Copyright © 2020 Hilvo, Vasile, Donato, Hurme and Laaksonen.)

Objective: Develop sample acceptability rules by determining the relationship between free hemoglobin level (hemolysis) and potassium or ionized calcium in blood gas samples collected intraoperatively., Design and Methods: Hemolysis was assessed visually or by H index for lithium heparin blood gas samples collected intraoperatively. During periods one and three this was done using two different rules for visual assessment of centrifuged lithium heparin plasma. During period two H index was measured for all visually hemolyzed samples on a Roche Cobas c501 analyzer to determine acceptability. Potassium and ionized calcium were measured in 75 lithium heparin whole blood samples on a Radiometer ABL90 to correlate H index and potassium or ionized calcium., Results: During period one 35 of 5808 (0.6%) blood gas samples had visual hemolysis levels exceeding tolerance for reporting of potassium. By switching to measured H index using a laboratory-established threshold, during period 2 we estimate that 171 of 5396 (3.2%) blood gas samples exceeded the H index threshold for reporting of potassium. In 75 intraoperative blood gas samples with H index and whole blood potassium and ionized calcium measured; we observed no relationship between H index and potassium or ionized calcium. During period 3 we switched to visual assessment of hemolysis with a greater tolerance for hemolysis; with only 3 of 5345 (0.06%) samples exceeding the new visual hemolysis threshold., Conclusion: For blood gas samples collected intraoperatively, there is no relationship between hemolysis and measured potassium or ionized calcium. The results suggest that only grossly hemolyzed intraoperative blood gas samples should be rejected for measurement of whole blood potassium and ionized calcium., (Copyright © 2019 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background & Aims: Patients with bile acid diarrhea (BAD) are identified based on increased levels of BAs in fecal samples collected over a 48-hr period while on a 100-gram fat diet (48-hr BA), retention of 75 Se-labeled homocholic acid taurine, or serum levels of C4 or FGF19. BAD increases fecal weight and colonic transit. We investigated whether results of tests for BAD associate with increased fecal weight and more rapid colonic transit over a 24- or 48-hr period in patients with irritable bowel syndrome with diarrhea (IBS-D). We also estimated the prevalence of increased 48-hr fecal BAs in patients with chronic diarrhea., Methods: We performed a retrospective study of 64 patients with IBS-D, 30 patients with IBS-constipation, 30 healthy volunteers (controls). We collected data on fecal weights (measured over a 48-hr period), colonic transit over a 24-hr period (measured by scintigraphy), and percentages of different BAs in stool samples. Colonic transit was measured as the geometric center (weighted average) of colonic counts on a scale of 1 (100% in ascending colon) to 5 (100% in stool). We performed area under the curve (AUC) analyses to assess the association between result of serum and stool tests and high fecal weight (>400g/48 hrs) or rapid colonic transit (>3.34, corresponding to isotope geometric center in sigmoid colon). We estimated the prevalence of increased 48-hr fecal BAs among 938 patients with chronic diarrhea., Results: Total fecal 48-hr BA alone, or in combination with percentage of primary fecal BAs, identified patients with increased fecal weight with an AUROC of 0.86. Percentage of primary fecal BA alone identified patients with increased fecal weight with an AUROC of 0.73. Total fecal 48-hr BA alone identified patients with increased colonic transit with an AUROC of 0.65 and percentage of primary fecal BA alone identified patients with increased colonic transit with an AUROC of 0.69; combined data on these features identified patients with increased colonic transit with an AUROC of 0.70. Serum level of C4 identified patients with increased colonic transit with an AUROC of 0.60. Primary BAs >10% identified patients with increased fecal weight (sensitivity 49% and specificity 91%) and rapid colonic transit (sensitivity 48% and specificity 87%). Among the patients with chronic diarrhea, 45.6% had fecal primary BAs >10% and 27% had increased total fecal BAs (>2337 μmol/48 hrs)., Conclusions: In a retrospective analysis of patients with IBS-D, we found percentage of primary BAs in fecal samples to provide an alternative to total fecal BAs in identification of patients with BAD or chronic diarrhea., (Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background: Biomarkers in irritable bowel syndrome (IBS) may guide targeted therapy in this multifactorial disease. It has been suggested that 75% accuracy and cost <$500 categorise biomarkers as cost-effective., Aim: To identify differences in faecal bile acids, faecal fat and fasting serum C4 (7a-hydroxy-4-cholesten-3-one) and fibroblast growth factor 19 (FGF19) among patients with IBS-D, IBS-C and healthy controls and to determine accurate, cost-effective biomarkers for clinically relevant diarrhoea and constipation., Methods: We assessed daily stool frequency and consistency (Bristol Stool Form Scale) from validated bowel diaries, 48 hours total and individual faecal bile acids, 48 hours faecal fat and weight, fasting serum C4 and FGF19, and colonic transit by scintigraphy from healthy volunteers (HV) and patients with IBS-D and IBS-C (Rome III criteria). We utilised multivariate logistic regression to determine biomarkers of clinically significant diarrhoea or constipation based on stool frequency, consistency and weight., Results: Among the 126 HV (44M/82F, 37.5 ± 10.9 years [SD]), 64 IBS-D (5M/59F, 41.9 ± 12.2 years), and 30 IBS-C (0M/30F, 44.6 ± 10 years) patients, there were significant differences between all groups in stool weight, frequency, and consistency; in addition, there were differences in colonic transit at 48 hours, faecal fat, and total and individual faecal bile acids between IBS-D and IBS-C. Reduced total and primary faecal bile acids and increased faecal lithocholic acid were significant predictors of decreased faecal weight, frequency and consistency with AUC > 0.82 (sensitivity >76%, specificity >72%). Total and primary faecal bile acids and faecal fat were significant predictors of increased stool weight, frequency and consistency with AUC > 0.71 (sensitivity >55%, specificity >74%).The faecal parameters had a 11.5 positive likelihood ratio in predicting elevated faecal weight., Conclusions: Faecal bile acids and faecal fat are cost-effective and accurate biomarkers associated with significant bowel dysfunction among IBS-D and IBS-C patients., (© 2019 John Wiley & Sons Ltd.)

Although U.S. Food and Drug Administration-approved and CLIA-waived point-of-care (POC) molecular systems are being implemented in routine clinical practice, instrument reliability, test performance in the hands of end users, and the potential for environmental contamination resulting from use of POC molecular systems have not been extensively evaluated. We performed a prospective evaluation of the Roche cobas Liat group A streptococcus (GAS) assay compared to routine real-time PCR. We evaluated test accuracy, instrument failure rate, and monitored for environmental contamination when testing was performed by minimally trained end users in an Express Care Clinic environment. The overall concordance of the Liat GAS assay with routine testing was 97.2% (455/468). The average Liat failure rate across three analyzers was 6.6% (33/501) (range, 3.7 to 11.6%), and no environmental contamination was detected during the course of the study. The cobas Liat platform and GAS assay demonstrated reliable performance in the end user setting and may serve as a rapid, POC option for routine diagnostic testing for certain infectious diseases, including GAS., (Copyright © 2019 American Society for Microbiology.)

Background: Several cases of biotin interference with laboratory testing have been reported in the literature. However, there are no publications discussing the extent of biotin use or plasma concentrations observed among the patient population. The objective of this study was to determine the prevalence of biotin consumption using two distinct methods: surveying the outpatient population using a questionnaire and quantifying biotin in plasma samples collected from patients presenting to the Emergency Department (ED)., Methods: Survey questionnaires (n = 4000) were distributed to Mayo Clinic outpatients over one week (July 10-14, 2017). Biotin was quantified in residual waste plasma samples collected for physician-ordered electrolyte panels from patients presenting to the ED (March 6-12, 2017 and March 26-April 4, 2017, n = 1442 unique patient samples)., Results: 1944 patients (972 female, 963 male, 9 no answer) with a median (interquartile range) age of 62 (49-72) years returned completed questionnaires (48.6%). From the completed surveys, 7.7% (95% CI, 6.6-8.9%) indicated biotin use. Quantitation of biotin in plasma samples from ED patients (n = 1442) revealed that 7.4% (95% CI, 6.2-8.9%) had concentrations at or above the lowest known threshold (10 ng/mL) for biotin interference in Roche Diagnostics immunoassay tests., Conclusions: According to our survey results, reported use of biotin was common. The range of biotin concentrations in ED patient samples highlights the magnitude of the biotin interference problem and identifies a population at risk for potential harm. These findings should guide laboratorians and clinicians in developing effective strategies to mitigate safety risks and in assessing biotin usage trends within their own patient populations., (Copyright © 2018 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Objective- Ceramides are sphingolipids involved with cellular signaling. Synthesis of ceramides occurs in all tissues. Ceramides accumulate within tissues and the blood plasma during metabolic dysfunction, dyslipidemia, and inflammation. Elevations of ceramides are predictive of cardiovascular mortality. We sought to verify the utility of plasma concentrations of 4 ceramides: N-palmitoyl-sphingosine [Cer(16:0)], N-stearoyl-sphingosine [Cer(18:0)], N-nervonoyl-sphingosine [Cer(24:1)], and N-lignoceroyl-sphingosine [Cer(24:0)] in predicting major adverse cardiovascular events in a diverse patient population referred for coronary angiography. Approach and Results- Plasma ceramides were measured in 495 participants before nonurgent coronary angiography. Coronary artery disease, defined as >50% stenosis in ≥1 coronary artery, was identified 265 (54%) cases. Ceramides were not significantly associated with coronary artery disease. Patients were followed for a combined primary end point of myocardial infarction, percutaneous intervention, coronary artery bypass, stroke, or death within 4 years. Ceramides were significantly predictive of outcomes after adjusting for age, sex, body mass index, hypertension, smoking, LDL (low-density lipoprotein) cholesterol, HDL (high-density lipoprotein) cholesterol, triglycerides, serum glucose, and family history of coronary artery disease. The fully adjusted per SD hazard ratios (95% confidence interval) were 1.50 (1.16-1.93) for Cer(16:0), 1.42 (1.11-1.83) for Cer(18:0), 1.43 (1.08-1.89) for Cer(24:1), and 1.58 (1.22-2.04) for the ceramide risk score. Conclusions- Elevated plasma concentrations of ceramides are independently associated with major adverse cardiovascular events in patients with and without coronary artery disease.

Background: Endogenous opioids, enkephalins, are known to increase with acute kidney injury. Since the mature pentapeptides are unstable, we evaluated the performance of an assay that measures proenkephalin 119-159 (PENK), a stable peptide formed concomitantly with mature enkephalins., Methods: PENK assay performance was evaluated on two microtiterplate/chemiluminescence sandwich immunoassay formats that required 18 or 1 h incubation times. PENK concentration was measured in plasma from healthy individuals to establish a reference interval and in patients with varied levels of kidney function and comorbidities to assess the association with measured glomerular filtration rate (mGFR) using iothalamate clearance., Results: Assay performance characteristics in plasma were similar between the assay formats. Limit of quantitation was 26.0 pmol/L (CV = 20%) for the 1 h assay and 17.3 pmol/L (CV = 3%) for the 18 h assay. Measurable ranges were 26-1540 pmol/L (1 h assay) and 18-2300 pmol/L (18 h assay). PENK concentrations are stable in plasma stored ambient to 10 days, refrigerated to at least 15 days, and frozen to at least 90 days. Results were comparable in paired SST serum and EDTA plasma. Age and sex were not associated with PENK concentrations in healthy individuals (reference interval: 36-97.5 pmol/L). Plasma PENK concentration correlated with mGFR. In a multivariate model PENK concentration, age, sex and transplant status were significant predictors of mGFR, and 49% of predicted GFR values fell within 30% of the mGFR., Conclusions: Both assay formats are accurate and precise for measuring clinically relevant PENK concentrations. The association of PENK concentration with mGFR is influenced by gender, age, and history of kidney transplantation. Future studies will determine if blood PENK can be used clinically to estimate GFR and/or detect AKI., (Copyright © 2018 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Imbalance of bile acids (BA) homeostasis in the gastrointestinal tract can lead to chronic diarrhea or constipation when BA in the colon are in excess or low, respectively. Since both disturbances of bowel function can result from other etiologies, identifying BA imbalance is important to tailor treatment strategies. Serum concentrations of 7-alpha-hydroxy-4-cholesten-3-one (7aC4), a precursor in bile acid synthesis, reflect BA homeostasis. Here we describe a method to accurately measure serum 7aC4 and evaluate the clinical utility in patients with diarrhea or constipation phenotypes., Methods: Serum 7aC4 is measured after acetonitrile protein precipitation using C18 liquid chromatography, tandem mass spectrometry, and deuterium-labeled 7aC4 internal standard. Assay performance including linearity, precision, and accuracy was assessed using waste serum samples. The reference interval was established in healthy individuals without BA-altering conditions or medications. Clinical performance was assessed in patients with irritable bowel syndrome., Results: The method precisely and accurately measured 7aC4 in human serum from 1.4-338ng/mL with no ion suppression or interference from related 7-keto-cholesterol. Central 95th percentile reference interval was 2.5-63.2ng/mL. Lower serum 7aC4 was found in patients with constipation with sensitivity/specificity of 79%/55% compared to healthy controls. Higher 7aC4 was found in patients with bile acid diarrhea (BAD) compared to those without BAD with sensitivity/specificity of 82%/53%., Conclusions: We have developed a sensitive and precise assay for measuring the concentration of 7aC4 in serum. The assay can be used to screen for diarrhea caused by bile acid malabsorption., (Copyright © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: The aim of this study was to evaluate the use of a glucose meter with surgical patients under general anesthesia in the operating room., Methods: Glucose measurements were performed intraoperatively on 368 paired capillary and arterial whole blood samples using a Nova StatStrip (Nova Biomedical, USA) glucose meter and compared with 368 reference arterial whole blood glucose measurements by blood gas analyzer in 196 patients. Primary outcomes were median bias (meter minus reference), percentage of glucose meter samples meeting accuracy criteria for subcutaneous insulin dosing as defined by Parkes error grid analysis for type 1 diabetes mellitus, and accuracy criteria for intravenous insulin infusion as defined by Clinical and Laboratory Standards Institute guidelines. Time under anesthesia, patient position, diabetes status, and other variables were studied to determine whether any affected glucose meter bias., Results: Median bias (interquartile range) was -4 mg/dl (-9 to 0 mg/dl), which did not differ from median arterial meter bias of -5 mg/dl (-9 to -1 mg/dl; P = 0.32). All of the capillary and arterial glucose meter values met acceptability criteria for subcutaneous insulin dosing, whereas only 89% (327 of 368) of capillary and 93% (344 of 368) arterial glucose meter values met accuracy criteria for intravenous insulin infusion. Time, patient position, and diabetes status were not associated with meter bias., Conclusions: Capillary and arterial blood glucose measured using the glucose meter are acceptable for intraoperative subcutaneous insulin dosing. Whole blood glucose on the meter did not meet accuracy guidelines established specifically for more intensive (e.g., intravenous insulin) glycemic control in the acute care environment.

Background: Solubility of Tumorigenicity 2 (sST2) is a novel biomarker that better stratifies risk of cardiovascular events (CVE) compared to cardiac troponin T(cTnT) in heart failure. We assessed the association of sST2 with the composite outcome of CVE and/or mortality compared to cTnT in kidney transplant candidates., Methods: 200 kidney transplant candidates between 2010 and 2013 were included. Elevated sST2 was defined as ≥30ng/ml, cTnT≥0.01 ng/ml., Results: Median age 53 (interquartile range (IQR) 42-61) years, 59.7% male and 82.0% white. 33.5% had history of CVE, 42.5% left ventricular hypertrophy (LVH) and 15.6% positive cardiac stress test. Elevated sST2 correlated with male gender, history of prior-transplants, CVE, positive stress test, LVH, elevated cTnT, anemia, hyperphosphatemia, increased CRP and non-transplanted status. Male gender, history of CVE and LVH were independent determinants of sST2. During 28 months (IQR 25.3-30), 7.5% died, 13.0% developed CVE and 19.0% developed the composite outcome. Elevated sST2 was associated with the composite outcome (hazard ratio = 1.76, CI 1.06-2.73, p = 0.029) on univariate analysis but not after adjusting for age, diabetes and cTnT (p = 0.068). sST2 did not change the risk prediction model for composite outcome after including age, diabetes, prior history of CVE and elevated cTnT., Conclusions: Increased sST2 level is significantly associated with variables associated with CVE in kidney transplant candidates. sST2 was associated with increased risk of the composite outcome of CVE and/or death but not independent of cTnT. Larger studies are needed to confirm these findings and determine whether sST2 has added value in CV risk stratification in this cohort of patients.

Background: A number of national and international guidelines recommend treatment to low-density lipoprotein cholesterol (LDL-C) <70 mg/dL. Comparing the performance of the Friedewald and a novel LDL-C estimate at these concentrations in a nationally representative and clinical cohorts can inform best practices., Objectives: The objectives of the study were to evaluate concordance between Friedewald-estimated LDL-C and novel-estimated LDL-C and compare with other atherogenic parameters when the estimated LDL-C is <70 mg/dL., Methods: Atherogenic lipid parameters were assessed in a cross-sectional analysis among participants with a Friedewald-estimated LDL-C <70 mg/dL from National Health and Nutrition Examination Survey (NHANES) 2011-2012 (n = 334), Johns Hopkins (n = 896), and Mayo Clinic (n = 1151). Novel LDL-C was estimated using an individualized factor to account for heterogeneity in the triglyceride to very low-density lipoprotein cholesterol ratio. Participants were classified as concordant if their LDL-C was <70 mg/dL by both equations and discordant if ≥70 mg/dL by the novel equation., Results: Among NHANES participants not on statin therapy, 10% had LDL-C <70 mg/dL by both the Friedewald and novel equations. Overall, 15% of participants from NHANES, 20% from Johns Hopkins, and 20% from Mayo Clinic had discordant LDL-C values. In all 3 cohorts, nearly one-fourth of participants in the discordant group had an LDL-C estimate of ≥80 mg/dL (ie, ≥10 mg/dL higher) by the novel equation. Compared with the concordant group, the discordant group had significantly higher median concentrations of non-high-density lipoprotein cholesterol (HDL-C; 101-104 mg/dL vs 74-79 mg/dL) and apolipoprotein B (apoB; 65-72 mg/dL vs 47-57 mg/dL). In NHANES, wherein statins use was recorded, a similarly higher atherogenic burden by non-HDL-C and apoB levels was observed on and off statin therapy in the discordant group., Conclusions: In a nationally representative sample, a hospital laboratory, and a reference laboratory, approximately one-fifth of individuals with Friedewald-estimated LDL-C <70 mg/dL have a value ≥70 mg/dL using the novel LDL-C equation. These individuals also have significantly higher non-HDL-C and apoB concentrations, conferring an increased risk for cardiovascular disease. Accordingly, ongoing use of Friedewald estimation may lead to the misclassification of high-risk individuals and subsequent under-utilization of lipid-lowering therapies. Further investigations are necessary to confirm these findings in patients using proprotein convertase subtilisin-kexin type 9 inhibitors., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)