Search

Background: Although P5 (preventive, personalized, predictive, participatory, psychocognitive) medicine and patient-focused healthcare are gaining ground in various healthcare areas, the diagnosis of antithrombin deficiency (ATD) is still based on crude diagnostic tests, clustering patients into clinically heterogeneous subgroups whereby relevant thrombophilia phenotypes may go unnoticed. Clinical pathways and the majority of evidence are based on these tests; therefore, generic treatment is still the norm., Objectives: To unravel the heterogeneity of ATD, a mass spectrometry (liquid chromatography coupled to multiple-reaction-monitoring mass spectrometry [LC-MRM-MS])-based test for antithrombin was developed allowing molecular characterization of the antithrombin proteoforms in patient plasma. This study provides the first insight into the tests' clinical performance., Methods: Plasma from 91 unrelated ATD patients and 41 patients with a congenital disorder of glycosylation affecting antithrombin glycosylation were characterized functionally, genetically, and analyzed by LC-MRM-MS. An established data analysis strategy was applied for quantitation and molecular characterization of antithrombin proteoforms., Results: The test recognized patients with a quantitative defect, discriminated between type I and type II ATD, and identified variant proteoforms. Overall, the diagnostic sensitivity for ATD was 100% for LC-MRM-MS compared with 81.1% by the functional test. Type II ATD, a subtype prone to misdiagnosis, revealed an even larger difference of 100% identification by LC-MRM-MS vs 56.8% by functional test., Conclusion: The qualitative and quantitative mass spectrometry-based AT-test can serve as a platform for investigating the molecular basis of the clinical heterogeneity of ATD. This "precision diagnostics" approach for ATD can lower diagnostic uncertainty and modernize the ATD diagnostic and clinical pathways., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: This was a cross-sectional study on the correlation between abdominal aortic calcification (AAC) and Modic changes (MC). Little is known regarding the etiology of MC in the lumbar spine. Currently, insufficient vascularization of the endplate has been proposed to contribute to the appearance of MC. Our objective was to investigate whether AAC, a marker for a poor vascular status, is associated with MC in patients suffering from degenerative disc disease., Methods: Radiologic images of patients (n = 130) suffering from degenerative lumbar disc disease were reviewed. Type and severity of MC were assessed using magnetic resonance images, and severity of AAC was evaluated using computed tomography images or fluoroscopy. Both items were dichotomized into minimal and relevant grades. The correlation between them was studied using Spearman's correlation test, with age as a covariate., Results: Of the patients, 113 (87%) demonstrated MC (31% type I, 63% type II, and 6% type III) (55% relevant grade), and 68% had AAC (44% relevant grade). Spearman statistical analysis revealed that AAC was correlated with age (P < 0.001), whereas MC were not (P = 0.142). AAC severity was significantly correlated with MC, remaining so after age adjustment (P < 0.05). While MC type I lacked correlation with AAC, MC type II were significantly correlated with AAC (0.288, P = 0.015); however, this association lost significance after adjusting for age (P = 0.057)., Conclusions: AAC and MC (mainly MC type II) are associated, indicating that reduced blood supply or even a poor systemic vascularization status due to atherosclerotic disease may play a role in the formation of MC. Future studies focusing on the etiology of MC should pay more attention to patients' vascular status and determinants of abdominal aorta calcification., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: Urinary tract infection (UTI) is common among older women. However, diagnosis is challenging because of frequent chronic lower urinary tract symptoms, cognitive impairment, and a high prevalence of asymptomatic bacteriuria (ASB). Current urine diagnostics lack specificity, leading to unnecessary treatment and antimicrobial resistance. This study aimed to evaluate the diagnostic accuracy of 12 urine biomarkers for diagnosing UTI in older women., Methods: In this case-control study, cases were women ≥65 years with ≥2 new-onset lower urinary tract symptoms, pyuria, and one uropathogen ≥10 4  CFU/mL. Controls were asymptomatic and classified as ASB (one uropathogen ≥10 5  CFU/mL), negative culture, or mixed flora. Urine biomarker concentrations were measured through liquid chromatography-mass spectrometry and ELISA. Diagnostic accuracy parameters of individual biomarkers and a biomarker model were derived from receiver operating characteristic curves., Results: We included 162 community-dwelling and institutionalized older women. Five urine inflammatory biomarkers demonstrated high discriminative ability (area under the curve ≥0.80): interleukin 6, azurocidin, neutrophil gelatinase-associated lipocalin, tissue inhibitor of metalloproteinases 2, and C-X-C motif chemokine 9. Azurocidin exhibited the highest diagnostic accuracy (sensitivity 86% [95% CI 75%-93%] and specificity 89% [95% CI 82%-94%] at 16.7 ng/mmol creatinine). A combined biomarker and pyuria model showed improved diagnostic accuracy in patients with UTI and ASB, compared with pyuria alone., Discussion: We identified several urine biomarkers that accurately differentiated older women with UTI from asymptomatic women, including ASB. These findings represent a potential advancement towards improved diagnostics for UTI in older women and warrant validation in a diverse population., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Antithrombin deficiency is a rare but severe disorder leading to high risk of thrombosis. The current clinical care pathway relies on activity tests, which only provide overall functional information on the in vitro activity of antithrombin. However, antithrombin exists in many different forms, also known as proteoforms, with varying clinical phenotypes. Precision diagnostics, facilitated by mass spectrometry, provides a strategy to improve patient diagnostics by molecular characterization., Objectives: To develop and analytically validate a mass spectrometry-based test for molecular characterization of antithrombin., Methods: The test was analytically validated based on predefined analytical performance specifications. The validation covered imprecision, carryover, linearity, stability, analytical specificity, a provisional reference interval, and an explorative method comparison., Results: The test passed the predefined analytical performance specifications with a mean within-laboratory imprecision of 5.9%, linearity between 0.08 and 2.58 μmol/L, and a provisional reference interval of 1.07 to 1.49 μmol/L. When measuring samples with a suspected quantitative deficiency, the test showed a good correlation with a commercial activity test (Pearson r  = 0.88)., Conclusion: The test passed the validation, and we now envision the use of the test for exploration of the clinical relevance of specific antithrombin proteoforms. Puzzling cases of antithrombin deficiency, for instance, due to ambiguous activity results or an atypical clinical presentation, can be investigated by the LC-MRM mass spectrometry test serving as an add-on to the activity test and providing a molecular diagnosis. Clinical studies are planned to investigate the potential of the test to improve antithrombin diagnostics. Furthermore, the molecular information gained using the test may aid in establishing better risk stratification and a basis for personalized medicine., (© 2023 The Authors.)

Background: The STAtins Reduce Thrombophilia trial showed that, in patients with prior venous thrombosis, rosuvastatin decreased various coagulation factor levels., Objectives: Here, we investigated the hypothesis that statins decrease coagulation factor levels through shared mechanisms of synthesis or regulatory pathways with apolipoproteins., Methods: We measured the levels of apolipoprotein (Apo)A-I, A-II, A-IV, (a), B-100, B-total, C-I, C-II, C-III, and E in patients (n = 126) randomized to 28 days of rosuvastatin use. We assessed the association between apolipoproteins and coagulation factors at baseline using linear regression. The mean difference in apolipoprotein levels between baseline and after 28 days of rosuvastatin use was determined through linear regression, adjusting for age, sex, and body mass index. Coagulation factors were added to this model to determine if the lowering of apolipoproteins by rosuvastatin was linked with coagulation factor levels., Results: At baseline, levels of all apolipoproteins, except Apo(a), were positively associated with FVII, FIX, and FXI. Apolipoproteins levels, except for ApoA-I, A-IV, and Apo(a), were decreased after 28 days of rosuvastatin. ApoB-100 showed the largest mean decrease of -0.43 g/L (95% CI = -0.46 to -0.40). The decrease in ApoC-I and C-III levels was associated with a decrease in FVII, whereas the decrease in apoA-II, B-100, and B-total was associated with a decrease in FXI. The decrease in apolipoproteins was neither associated with FVIII or vWF decrease nor with endogenous thrombin potential changes., Conclusions: Rosuvastatin decreases the level of several apolipoproteins, but this decrease was associated only with a decrease in FVII and XI and not with FVIII/vWF., (© 2023 The Author(s).)

Background: Mutations in genes encoding lipoprotein lipase (LPL) or its regulators can cause severe hypertriglyceridemia (HTG). Thus far, the effect of genetic HTG on the lipid profile has been mainly determined via conventional techniques., Objective: To show detailed differences in the (apo)lipoprotein profile of patients with genetic HTG by combining LC-MS and NMR techniques., Methods: Fasted serum from 7 patients with genetic HTG and 10 normolipidemic controls was used to measure the concentration of a spectrum of apolipoproteins by LC-MS, and to estimate the concentration and size of lipoprotein subclasses and class-specific lipid composition using NMR spectroscopy., Results: Patients with genetic HTG compared to normolipidemic controls had higher levels of apoB48 (fold change [FC] 11.3, P<0.001), apoC-I (FC 1.5, P<0.001), apoC-II (FC 4.3, P=0.007), apoC-III (FC 3.4, P<0.001), and apoE (FC 4.3, P<0.001), without altered apoB100. In addition, patients with genetic HTG had higher concentrations of TG-rich lipoproteins (i.e., chylomicrons and very low-density lipoproteins [VLDL]; FC 3.0, P<0.001), but lower LDL (FC 0.4, P=0.001), of which medium and small-sized LDL particles appeared even absent. While the correlation coefficient between NMR and enzymatic analysis in normolipidemic controls was high, it was considerably reduced in patients with genetic HTG., Conclusion: The lipoprotein profile of patients with genetic HTG is predominated with large lipoproteins (i.e., chylomicrons, VLDL), explaining high levels of apoC-I, apoC-II, apoC-III and apoE, whereas small atherogenic LDL particles are absent. The presence of chylomicrons in patients with HTG weakens the accuracy of the NMR-based model as it was designed for normolipidemic fasted individuals., Competing Interests: Declarations of Competing Interest None, (Copyright © 2022. Published by Elsevier Inc.)

With the upcoming EU regulation on the use of in-vitro diagnostic devices, a critical evaluation of the current status of our in-house developed LC-MS/MS methods is timely and of great relevance. Recently, much attention has been devoted to the need for better specification of analytical and clinical performance. Appropriate reporting of the actual achieved analytical performance is an important determinant of the clinical performance and subsequent clinical effectiveness of a test. We advocate for the application of CLSI C62-A guidelines for method validation and suggest some adaptations for analytical validation of in-house developed LC-MS/MS methods for endogenous substances. Additionally, we underline the importance of well-equipped reviewers and standardized method description, including the presentation of figural evidence of obtained method performance. Achieving this ensures future quality of our in-house developed LC-MS/MS methods., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: International normalized ratio (INR) is traceable to World Health Organization (WHO) International Standards for thromboplastins. International Standards must be used with a manual tilt tube technique (MTT) for prothrombin time (PT) determination. An important part of the total variability of INR is due to poor harmonization of MTT across WHO reference laboratories., Objectives: To determine the origins of PT differences between operators performing MTT and to develop a harmonized MTT., Methods: Two workshops were held where WHO reference laboratory operators could compare their PTs using MTT and the same equipment. A harmonized MTT was used by seven operators in the second workshop., Results: Differences have been observed in tilting frequency and in the height of pipetting plasma in the test tube. At the beginning of the first workshop, the tilting cycle time varied between 1.1 and 2.7 seconds. The mean PT of normal plasma obtained by pipetting plasma at the top of the tube was 14.3 seconds but was 12.9 seconds when plasma was pipetted at the bottom of the tube. When using the harmonized MTT for WHO International Standard rTF/16, the differences between operators were not greater than 1.1 seconds in normal plasma, and not greater than 1.3 seconds in patient plasma with average INR of 3.0. INR between-operator coefficient of variation was 2.3%., Conclusion: Application of a harmonized MTT in three reference laboratories resulted in substantial reduction of between-operator variation of PT and INR. The harmonized MTT is proposed as Candidate Reference Measurement Procedure., (2020 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals LLC on behalf of International Society on Thrombosis and Haemostasis.)

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (=total - HDL cholesterol) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDL cholesterol is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDL cholesterol shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a)-cholesterol is part of measured or calculated LDL cholesterol and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDL cholesterol decline poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDL cholesterol or apolipoprotein B, especially in patients with mild-to-moderate hypertriglyceridemia (2-10 mmol/L). Non-HDL cholesterol includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apolipoprotein B measurement can detect elevated LDL particle numbers often unidentified on the basis of LDL cholesterol alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20-100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Introduction: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation and variable renal function decline that frequently leads to end-stage renal failure. With the advent of renoprotective treatment, there is renewed interest in noninvasive biomarkers to help identify patients at risk of rapid disease progression at early stages. Urinary tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) have been validated as early markers of acute kidney injury. Because these markers are associated with tubular damage, we studied the performance of both markers in a cohort with chronic tubular pathology. We investigated whether these biomarkers may be useful to evaluate disease severity in ADPKD., Methods: In a cross-sectional analysis, we measured TIMP-2 and IGFBP7 in stored spot urine samples of patients with ADPKD with various stages of chronic kidney disease (CKD) and healthy controls by enzyme-linked immunosorbent assay. Renal function was estimated using the CKD-Epidemiology Collaboration equation. Patients were stratified according to the Kidney Disease Outcomes Quality Initiative classification for CKD. In a subset of patients, total kidney volume (TKV; using magnetic resonance imaging [MRI]) was measured., Results: In 296 patients with ADPKD (45.5 ± 11.5 years, 51.0% female, serum creatinine 106 [85-147] μmol/l), urine levels of TIMP-2 and IGFBP7 were not increased or tended to be lower as compared with 71 healthy controls (46.5 ± 18.5 years, 72.6% female). The levels did not differ across CKD stages, which remained so after correcting for urine creatinine or osmolality, and for age, sex, and urine protein in multivariable analyses., Conclusions: Urinary levels of TIMP-2 and IGFBP7 were not higher in patients with ADPKD, and did not correlate with disease severity.

Background: While the overall acute myocardial infarction rates declined in women and men, premature acute myocardial infarction rates remained stable in men and increased in women., Objective: The purpose of this study was to assess whether baseline apolipoprotein (apo) levels, clinical characteristics, and follow-up of patients with very premature coronary artery disease (CAD) could provide novel clues for the identification of high-risk individuals., Methods: Apos were measured with a validated quantification liquid chromatography-mass spectrometry method in a well-defined cohort of 38 patients aged ≤45 years admitted with acute ST-segment elevation myocardial infarction., Results: Mean age was 39.8 ± 4.6 years and 24% was female. Four of these patients (11%) had apoCII levels ≤5.0 mg/L. Compared with the very premature CAD group with apoCII > 5 mg/L, the patients with apoCII levels ≤5.0 mg/L were all females, tended to be younger (35.8 ± 8.4 years vs 40.3 ± 3.9 years, P = .063), had more often a family history of cardiovascular disease ≤65 years (P = .034) and a significantly lower Framingham risk score (P = .001). They presented with normal triglyceride levels, and had lower low-density lipoprotein cholesterol, apoB 100 , and apoE levels. Corrected for differences in risk profile, apoCII ≤ 5 mg/L was associated with increased risk of 10-years reinfarction or revascularization (hazard ratio 7.9 [95% confidence interval 1.5-41.6], P = .015)., Conclusions: In 38 patients with very premature CAD, 11% were found to have low apoCII levels (≤5.0 mg/L) with normal triglyceride levels. Despite their low a priori risk for CAD, these patients presented with ST-segment elevation myocardial infarction and had a high relative risk of 10-year reinfarction or revascularization. This particular phenotype of relatively young female patients with CAD is not recognized earlier and deserves further study., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: Cold exposure and β3-adrenergic receptor agonism, which both activate brown adipose tissue, markedly influence lipoprotein metabolism by enhancing lipoprotein lipase-mediated catabolism of triglyceride-rich lipoproteins and increasing plasma high-density lipoprotein (HDL) levels and functionality in mice. However, the effect of short-term cooling on human lipid and lipoprotein metabolism remained largely elusive., Objective: The objective was to assess the effect of short-term cooling on the serum lipoprotein profile and HDL functionality in men., Methods: Body mass index-matched young, lean men were exposed to a personalized cooling protocol for 2 hours. Before and after cooling, serum samples were collected for analysis of lipids and lipoprotein composition by 1 H-nuclear magnetic resonance. Adenosine triphosphate-binding cassette A1 (ABCA1)-mediated cholesterol efflux capacity of HDL was measured using [ 3 H]cholesterol-loaded ABCA1-transfected Chinese hamster ovary cells., Results: Short-term cooling increased serum levels of free fatty acids, triglycerides, and cholesterol. Cooling increased the concentration of large very low-density lipoprotein (VLDL) particles accompanied by increased mean size of VLDL particles. In addition, cooling enhanced the concentration of small LDL and small HDL particles as well as the cholesterol levels within these particles. The increase in small HDL was accompanied by increased ABCA1-dependent cholesterol efflux in vitro., Conclusions: Our data show that short-term cooling increases the concentration of large VLDL particles and increases the generation of small LDL and HDL particles. We interpret that cooling increases VLDL production and turnover, which results in formation of surface remnants that form small HDL particles that attract cellular cholesterol., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: The introduction of new biomarkers can lead to inappropriate utilization of tests if they do not fill in existing gaps in clinical care. We aimed to define a strategy and checklist for identifying unmet needs for biomarkers., Methods: A multidisciplinary working group used a 4-step process: 1/ scoping literature review; 2/ face-to-face meetings to discuss scope, strategy and checklist items; 3/ iterative process of feedback and consensus to develop the checklist; 4/ testing and refinement of checklist items using case scenarios., Results: We used clinical pathway mapping to identify clinical management decisions linking biomarker testing to health outcomes and developed a 14-item checklist organized into 4 domains: 1/ identifying and 2/ verifying the unmet need; 3/ validating the intended use; and 4/ assessing the feasibility of the new biomarker to influence clinical practice and health outcome. We present an outcome-focused approach that can be used by multiple stakeholders for any medical test, irrespective of the purpose and role of testing., Conclusions: The checklist intends to achieve more efficient biomarker development and translation into practice. We propose the checklist is field tested by stakeholders, and advocate the role of the clinical laboratory professional to foster trans-sector collaboration in this regard., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, we have followed up on previous liquid chromatography (LC) multiple reaction monitoring (MRM) mass spectrometry (MS) approaches for measurement of apolipoprotein (apo) A-I and apo B100 in serum aiming for implementation of a multiplexed assay in a clinical chemistry laboratory with full metrological traceability. Signature peptides were selected and detected by dynamic MRM, and stable isotope labeled (SIL)-peptides were used as internal standards. Five apo A-I and four apo B100 peptides were measured in serum digests with linearity (R(2)>0.992) in the physiologically relevant concentration ranges. Linearity with regard to protein concentration was ascertained at five concentration levels (R(2)>0.926 and R(2)>0.965, for the apo A-I and apo B100 peptides, respectively). Three native value-assigned sera were used as external calibrators for further method verification. Imprecision values on sample preparation and LC-MS/MS acquisition were below the established minimal specifications for apo A-I and apo B100 (5.0% and 5.3%, respectively). Correlation of LC-MS/MS results with immunoturbidimetric assay results, for normo- and hypertriglyceridemic samples, showed R(2)>0.944 for apo A-I and R(2)>0.964 for apo B100. This LC-MS/MS method has potential for clinical application in normo- and dyslipidemic patients., Biological Significance: Measurement of apo A-I and apo B100 may offer an alternative to high and low density lipoprotein cholesterol (HDL-c and LDL-c) methods for cardiovascular disease risk assessment in dyslipidemic patients [1]. An LC-MS/MS method for apo A-I and apo B100 has the advantage of antibody independent and specific detection of protein signature peptides. The introduction of an LC-MS/MS method for apo A-I and apo B100 can serve as an example for many existing and newly developed (multiplex) biomarker methods in quantitative clinical chemistry proteomics (qCCP). Such LC-MS/MS methods should meet basic clinical chemistry principles with regard to test evaluation [2]. Criteria for imprecision should be pre-defined, e.g., based on biological variation. The use of commutable and traceable serum-based calibrators will improve inter-laboratory reproducibility of LC-MS/MS methods and may contribute to a more rapid transition of biomarker discovery to clinical utility with benefit for the patient treatment and improvement of general health care., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Introduction: In the modern healthcare service, patients receive care in multiple hospitals and healthcare settings. Therefore, harmonization of results from different methods and instruments, both between and within laboratories, is of the utmost importance. The present pilot study aims to test the use of a Category 1 EQA scheme across four European countries by assessing the current level of equivalence of test results., Method: This work was led by the Dutch External Quality Assurance Scheme SKML and involved 28 laboratories from three regions in the UK, Spain and Portugal, and 120 laboratories from The Netherlands. A set of six commutable samples, targeted with reference methods, were circulated and 18 biochemistry analytes were tested., Results and Conclusions: The Total Error (TE) score, defined as the probability (%) that results are within the Total Error Acceptable (TEA) limits, for the eighteen analytes was calculated. Our data show that there is a need for further harmonization of laboratory data, in particular for electrolytes (calcium, chloride, magnesium, sodium), enzymes (ALT, amylase, AST, LDH), lipids (HDL-cholesterol), and for substrates (creatinine, total protein). Lack of performance consistency between instruments was seen for most analytes. The lack of harmonization is still present despite manufacturer claims of established traceability., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Despite international standardization programs for LDLc and HDLc measurements, results vary significantly with methods from different manufacturers. We aimed to simulate the impact of analytical error and hypertriglyceridemia on HDLc- and LDLc-based cardiovascular risk classification., Methods: From the Dutch National EQA-2012 external quality assessment of 200 clinical laboratories, we examined data from normotriglyceridemic (∼ 1 mmol/l) and hypertriglyceridemic (∼ 7 mmol/l) serum pools with lipid target values assigned by the Lipid Reference Laboratory in Rotterdam. HDLc and LDLc were measured using direct methods of Abbott, Beckman, Siemens, Roche, Olympus, or Ortho Clinical Diagnostics. We simulated risk reclassification using HDL- and sex-specific SCORE multipliers considering two fictitious moderate-risk patients with initial SCORE 4% (man) and 3% (woman). Classification into high-risk treatment groups (LDLc >2.50 mmol/l) was compared between calculated LDLc and direct LDLc methods., Results: Overall HDLc measurements in hypertriglyceridemic serum showed negative mean bias of -15%. HDL-multipliers falsely reclassified 70% of women and 43% of men to a high-risk (SCORE >5%) in hypertriglyceridemic serum (P < 0.0001 vs. normotriglyceridemic serum) with method-dependent risk reclassifications. Direct LDLc in hypertriglyceridemic serum showed positive mean bias with Abbott (+16%) and Beckman (+14%) and negative mean bias with Roche (-7%). In hypertriglyceridemic serum, 57% of direct LDLc measurements were above high-risk treatment goal (2.50 mmol/l) vs. 29% of direct LDLc (33% of calculated LDLc) in normotriglyceridemic sera., Conclusion: LDLc and HDLc measurements are unreliable in severe hypertriglyceridemia, and should be applied with caution in SCORE risk classification and therapeutic strategies., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Regulators and healthcare payers are increasingly demanding evidence that biomarkers deliver patient benefits to justify their use in clinical practice. Laboratory professionals need to be familiar with these evidence requirements to better engage in biomarker research and decisions about their appropriate use. This paper by a multidisciplinary group of the European Federation of Clinical Chemistry and Laboratory Medicine describes the pathway of a laboratory assay measuring a biomarker to becoming a medically useful test. We define the key terms, principles and components of the test evaluation process. Unlike previously described linearly staged models, we illustrate how the essential components of analytical and clinical performances, clinical and cost-effectiveness and the broader impact of testing assemble in a dynamic cycle. We highlight the importance of defining clinical goals and how the intended application of the biomarker in the clinical pathway should drive each component of test evaluation. This approach emphasizes the interaction of the different components, and that clinical effectiveness data should be fed back to refine analytical and clinical performances to achieve improved outcomes. The framework aims to support the understanding of key stakeholders. The laboratory profession needs to strengthen collaboration with industry and experts in evidence-based medicine, regulatory bodies and policy makers for better decisions about the use of new and existing medical tests., (© 2013.)

Background: Equivalence of results among laboratories is a major mission for medical laboratories. Monitoring of test equivalence is structurally integrated in the Dutch External Quality Assessment (EQA) scheme since 2005. Commutable poolsera, single donation "spy" sera and biological variance tolerance limits have been introduced in the EQA scheme for evaluation of the degree of test equivalence and its determinants., Methods: In the annual cycle scheme 24 samples, covering the (patho)physiological measuring range for 17 analytes, are assayed by 220 participating laboratories at biweekly intervals. Test equivalence was evaluated by calculating overall median interlaboratory coefficients of variation (CVs) and its bias and imprecision components. Data from 2005 and 2010 schemes are evaluated to investigate trends in performance and success of standardization efforts., Results: Overall median interlaboratory CVs in 2010 were mostly better than in 2005. Median interlaboratory CVs became <5% for electrolytes and substrates, and <10% for enzymes. Improvement in median interlaboratory CVs over these five years is mainly explained by improved method standardization, especially for enzymes and creatinine., Conclusion: The Dutch EQA-program proves to be a powerful instrument to evaluate test equivalence. It allows monitoring standardization efforts in a highly effective way and gives insight into remaining standardization potential., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In this study temperature-dependent instability of the cTnI subunit of the three-protein complex NIST SRM2921 was demonstrated using a mass spectrometric tryptic peptide mapping approach. The results were compared to the cTnI subunit obtained as a protein standard from Calbiochem with identical amino acid sequence. Both the three-protein complex from NIST as well as the cTnI subunit were incubated at elevated temperatures and then evaluated with respect to the primary sequence. The corresponding peptide maps were analyzed using LC-MS/MS. From a Mascot database search in combination with "semiTrypsin" tolerance it was found that two peptide backbone cleavages had occurred in subunit cTnI in NIST SRM2921 material upon incubation at 37°C, namely between amino acids at 148/149 and 194/195. The Calbiochem standard did not show increased levels of "unexpected" peptides in tryptic peptide maps. One of the two peptide backbone cleavages could also be monitored using a "single-step" MALDI-MS approach, i.e. without the need for peptide separation. The amount of degradation appeared rather constant in replicate temperature-instability experiments. However, for accurate quantification internal labelled standards are needed., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objective: Recently, salivary alpha-amylase (sAA) has been proposed as a suitable index for sympathetic activity and dysregulation of the autonomic nervous system (ANS). Although determinants of sAA have been described, they have not been studied within the same study with a large sample size without potential disturbances of psychopathology. In this paper, we report about correlates of evening sAA in saliva., Methods: In 487 participants (mean age=42.9years, 59.8% female) without lifetime psychiatric disorders from the Netherlands Study of Depression and Anxiety (NESDA), sociodemographic, health and sampling determinants of sAA levels were examined using multivariable linear regression analysis. sAA was measured in two saliva samples that participants collected in the late evening, at 22:00h and 23:00h, after which these were averaged., Results: In multivariate analysis, age (β=0.20, p<0.001) and daily alcohol intake (β=-0.13, p=0.01) were independent determinants of evening sAA levels. Gender, allergy or lung disease, and the use of oral contraceptives were univariate correlates, but no longer associated with sAA in the multivariate model., Conclusions: Age and alcohol use were identified as potential confounding factors that should be taken into account in epidemiologic studies that examine the ANS function using sAA., (Copyright © 2012 Elsevier B.V. All rights reserved.)