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The standardization of cystatin C (CysC) measurement has received increasing attention in recent years due to its importance in estimating glomerular filtration rate (GFR). Mass spectrometry-based assays have the potential to provide an accuracy base for CysC measurement. However, a precise, accurate and sustainable LC–MS/MS method for CysC is still lacking. The developed LC–MS/MS method quantified CysC by detecting signature peptide (T3) obtained from tryptic digestion. Stable isotope labeled T3 peptide (SIL-T3) was spiked to control matrix effects and errors caused by liquid handling. The protein denaturation, reduction and alkylation procedures were combined into a single step with incubation time of 1 h, and the digestion lasted for 3.5 h. In the method validation, digestion time-course, imprecision, accuracy, matrix effect, interference, limit of quantification (LOQ), carryover, linearity, and the comparability to two routine immunoassays were evaluated. No significant matrix effect or interference was observed with the CysC measurement. The LOQ was 0.21 mg/L; the within-run and total imprecision were 1.33–2.05 % and 2.18–3.90 % for three serum pools (1.18–5.34 mg/L). The LC–MS/MS method was calibrated by ERM-DA471/IFCC and showed good correlation with two immunoassays traceable to ERM-DA471/IFCC. However, significant bias was observed for immunoassays against the LC–MS/MS method. The developed LC–MS/MS method is robust and simpler and holds the promise to provide an accuracy base for routine immunoassays, which will promote the standardization of CysC measurement. [ABSTRACT FROM AUTHOR]

Clinical biomarker research is growing at a fast pace, particularly in the cardiovascular field, due to the demanding requirement to provide personalized precision medicine. The lack of a distinct molecular signature for each cardiovascular derangement results in a one-size-fits-all diagnostic and therapeutic approach, which may partially explain suboptimal outcomes in heterogeneous cardiovascular diseases (e.g., heart failure with preserved ejection fraction). A multidimensional approach using different biomarkers is quickly evolving, but it is necessary to consider pre-analytical variables, those to which a biological sample is subject before being analyzed, namely sample collection, handling, processing, and storage. Pre-analytical errors can induce systematic bias and imprecision, which may compromise research results, and are easy to avoid with an adequate study design. Academic clinicians and investigators must be aware of the basic considerations for biospecimen management and essential pre-analytical recommendations as lynchpin for biological material to provide efficient and valid data. [ABSTRACT FROM AUTHOR]

Background: Definitive data to establish if the use of the WHO International Standard (IS) 03/178 as a common calibrator of commercial measuring systems (MSs) has improved the harmonization of serum total folate (tFOL) measurements to a clinically suitable level are lacking. Here, we report the results of an intercomparison study aimed to verify if the current inter-assay variability is acceptable for clinical application of tFOL testing. Methods: After confirming their commutability, the IS 03/178 and National Institute for Standards and Technology SRM 3949 L1 were used for evaluating the correctness of traceability implementation by manufacturers and the MSs trueness, respectively. The inter-assay agreement was verified using 20 patient pools. The measurement uncertainty (U) of tFOL measurements on clinical samples was also estimated. An outcome-based model for defining desirable performance specifications for bias and imprecision for serum tFOL measurements was applied. Results: The majority of evaluated MSs overestimated the WHO IS value of +5% or more with the risk to produce an unacceptably high number of false-negative results in clinical practice. The mean inter-assay CV on all pools and on those with tFOL values >3.0 μg/L (n = 15) was 12.5% and 7.1%, respectively. In neither case the goal of 3.0% was fulfilled. The residual bias resulted in an excessive U of tFOL measurement on clinical samples. Conclusions: The implementation of traceability of tFOL MSs to the WHO IS 03/178 is currently inadequate, resulting in an inter-assay variability that does not permit the use of a common threshold for detecting folate deficiency. [ABSTRACT FROM AUTHOR]

Acute myocardial infarction is the most common cause of morbidity and mortality in the world. Cardiac troponin measurements play a key role in the diagnosis. However, preanalytical errors as a result of the presence of fibrin or interference due to conditions such as heterophile antibody positivity may cause erroneously high results. Such errors may result in invasive procedures, such as angiography, which may add unnecessary risk. In our hospital, high-sensitivity troponin- I (hs-TnI) was routinely analyzed using a serum separator tube (reference value: female <15.5 pg/mL, male <34.2 pg/mL). This report describes the cases of 2 patients with a false initial troponin measurement: a 19-year-old male patient and a 55-year-old female patient. The hs-TnI value of the male patient was initially measured as 55.5 pg/mL. After the analysis, it was noted that the sample contained fibrin. The sample was centrifuged again and the TnI result was 1.8 pg/mL. Similarly, the TnI result of the female patient was first measured as 90.2 pg/mL. When it was observed that there was fibrin present, the sample was recentrifuged. The revised result was 2.4 pg/mL. The laboratory staff were trained on preanalytical errors, and the use of lithium heparin tubes was implemented in the laboratory as an additional means to eliminate the problem of fibrin interference. [ABSTRACT FROM AUTHOR]

Background: Serum uric acid is a critical clinical indicator, and results without equivalence among laboratories cause troubles for disease diagnosis and patient management. External quality assessment (EQA) is a common tool for enhancing harmonization/standardization, therefore, the National Center for Clinical Laboratories in China has initiated a category 1 EQA for serum uric acid measurement since 2010 for evaluating its process of standardization. Methods: Commutable EQA samples with target values assigned by reference measurement procedures were sent to participant laboratories. Both concentrations were measured 15 times in 3 days then means and intra-laboratory coefficient of variations (CVs) were reported. Biological variation criteria were used for analysis with CLIA88 criteria as a comparison. Results: A total of 1250 laboratories participated in EQA programs from 2010 to 2017, pass rates calculated according to desirable specifications in biological variation database were on a rise overall and inter-laboratory mean bias and CVs were on a decrease. Homogeneous systems showed better inter-laboratory CVs and pass rates than heterogeneous systems. For the mostly used measurement systems; Abbott, Beckman, Roche Modular, Siemens and Hitachi showed desirable performances other than Roche Cobas, according to biological variation criteria. Conclusions: Our study provides reliable information on the standardization of measurement procedures for serum uric acid for manufacturers and laboratories. Further improvements for standardization are still needed to make laboratories more patient-centered. [ABSTRACT FROM AUTHOR]

The constrained economic context leads laboratories to centralize their routine analyses on high-throughput platforms, to which blood collection tubes are sent from peripheral sampling sites that are sometimes distantly located. Providing biochemistry results as quickly as possible implies to consolidate the maximum number of tests on a minimum number of blood collection tubes, mainly serum tubes and/or tubes with anticoagulants. However, depending on the parameters and their pre-analytical conditions, the type of matrix - serum or plasma - may have a significant impact on results, which is often unknown or underestimated in clinical practice. Importantly, the matrix-related effects may be a limit to the consolidation of analyses on a single tube, and thus must be known by laboratory professionals. The purpose of the present critical review is to put forward the main differences between using serum and plasma samples on clinical biochemistry analyses, in order to sensitize laboratory managers to the need for standardization. To enrich the debate, we also provide an additional comparison of serum and plasma concentrations for approximately 30 biochemistry parameters. Properties, advantages, and disadvantages of serum and plasma are discussed from a pre-analytical standpoint - before, during, and after centrifugation - with an emphasis on the importance of temperature, delay, and transport conditions. Then, differences in results between these matrices are addressed for many classes of biochemistry markers, particularly proteins, enzymes, electrolytes, lipids, circulating nucleic acids, metabolomics markers, and therapeutic drugs. Finally, important key-points are proposed to help others choose the best sample matrix and guarantee quality of clinical biochemistry assays. Moreover, awareness of the implications of using serum and plasma samples on various parameters assayed in the laboratory is an important requirement to ensure reliable results and improve patient care. [ABSTRACT FROM AUTHOR]

Background: Estimating equations are recommended by clinical guidelines as the preferred method for assessment of glomerular filtration rate (GFR). The aim of the study was to compare population-based prevalence estimates of decreased kidney function in Germany defined by an estimated GFR (eGFR) <60 ml/min/1.73m2 using different equations.Methods: The study included 7001 participants of the German Health Interview and Examination Survey for Adults 2008-2011 (DEGS1) for whom GFR was estimated using the Modification of Diet in Renal Disease study equation (MDRD), the revised Lund-Malmö equation (LM), the Full Age Spectrum creatinine equation (FAScre), the Chronic Kidney Disease Epidemiology Collaboration equations with creatinine and cystatin C (CKD-EPIcrecys), with creatinine (CKD-EPIcre) and with cystatin C (CKD-EPIcys). Bland-Altman plots were used to evaluate the agreement between the equations.Results: Prevalence estimates of decreased kidney function were: 2.1% (CKD-EPIcys), 2.3% (CKD-EPIcrecys), 3.8% (CKD-EPIcre), 5.0% (MDRD), 6.0% (LM) and 6.9% (FAScre). The systematic differences between the equations were smaller by comparing either equations that include serum cystatin C or equations that include serum creatinine alone and increased considerably by increasing eGFR.Conclusions: Prevalence estimates of decreased kidney function vary considerably according to the equation used for estimating GFR. Equations that include serum cystatin C provide lower prevalence estimates if compared with equations based on serum creatinine alone. However, the analysis of the agreement between the equations according to eGFR provides evidence that the equations may be used interchangeably among persons with pronounced decreased kidney function. The study illustrates the implications of the choice of the estimating equation in an epidemiological setting. [ABSTRACT FROM AUTHOR]

The review presents a chronological development of procedures for determining the concentrations of total protein and albumin; total concentration of globulins; concentrations of subfractions, classes, and subclasses of globulins; and total concentrations of globulin subclasses in human blood. A brief overview of these procedures and the results of their comparative tests in medical examination of patients are given. The considered procedures are systematized; their advantages and disadvantages are discussed. It is noted that procedures for measuring the concentration of total protein, albumin, and globulin classes in plasma, serum, and whole blood are widely used in modern clinical diagnostic laboratories when performing routine assays. The concentrations of globulin subclasses and total concentrations of globulin subclasses in blood are mainly determined in biomedical research. Procedures for measuring the concentration of total globulins and globulin subfractions in plasma and serum are of historical importance and now are barely applied in clinical and diagnostic laboratories. [ABSTRACT FROM AUTHOR]

The review presents the chronological development of procedures for determining the concentrations of total protein and albumin; total concentration of globulins; concentrations of subfractions, classes, and subclasses of globulins; and total concentrations of globulin subclasses in human blood. A brief overview of these procedures and the results of their comparative tests in medical examination of patients are given. The considered procedures are systematized; their advantages and disadvantages are discussed. It is noted that procedures for measuring the concentration of total protein, albumin, and globulin classes in plasma, serum, and whole blood are widely used in modern clinical diagnostic laboratories when performing routine assays. The concentrations of globulin subclasses and total concentrations of globulin subclasses in blood are mainly determined in biomedical research. Procedures for measuring the concentration of total globulins and globulin subfractions in plasma and serum are of historical importance and now are barely applied in clinical and diagnostic laboratories. [ABSTRACT FROM AUTHOR]

Background: Acute kidney injury (AKI) has been associated with high morbidity and mortality rates among critically ill children. Cystatin C is a protease inhibitor, and studies have shown that it is a promising marker for the early diagnosis of AKI. Our goal in this study was to assess whether serum cystatin C could serve as an accurate marker for the diagnosis of AKI.Methods: This prospective study was undertaken in the pediatric intensive care unit at King Abdulaziz University Hospital. Serum creatinine and serum cystatin C levels were both measured in patients on admission (0 h) and at 6, 12, and 24 h after admission. AKI was diagnosed according to the modified pRIFLE criteria. Receiver operating characteristic (ROC) curve analysis was performed to assess the utility of serum cystatin C for diagnosing AKI.Results: A total of 62 patients were enrolled in this study, and 32 were diagnosed with AKI according to the modified pRIFLE criteria (51.4 %). The area under the ROC curve for serum cystatin indicated that it was a good marker for the diagnosis of AKI at 0, 6, 12 and 24 h, with sensitivities of 78, 94, 94 and 83 %, respectively. However, the specificities of serum cystatin C at 0, 6, 12, and 24 h were 57, 57, 60 and 50 %, respectively. The optimal cutoff value was 0.645 mg/L. The area under the ROC for serum creatinine showed sensitivities of 50, 65.4, 69.2 and 57.7 % and specificities of 67.7, 70, 60 and 70 % at 0, 6, 12 and 24 h, respectively. The optimal cutoff value for serum creatinine was 30 μmol/l. Comparisons of ROC curves revealed that serum cystatin C was superior to serum creatinine for the diagnosis of AKI at 12 h (p = 0.03), but no differences were detected at 0, 6 or 24 h.Conclusion: Serum cystatin is a sensitive, but not a specific, marker for the diagnosis of AKI in critically ill children. [ABSTRACT FROM AUTHOR]

The chronological development of destructive and nondestructive methods designed to determine the glucose concentration in plasma, serum, and whole blood is presented in the review. Destructive procedures are divided into spectrophotometric, spectrofluorimetric, diffraction, amperometric, potentiometric, conductometric, chromatographic, gas chromatographic-mass spectrometric, titrimetric, and calorimetric types, as well as reflectance photometry. A brief overview of these methods and the results of comparative tests are given; the procedures are systematized. It is noted that certain types of enzymatic spectrophotometric and amperometric methods have received wide acceptance for analyzes in clinical diagnostic laboratories. Outside clinical laboratories, enzymatic amperometric and spectrophotometric procedures and reflectance photometry procedures using test strips are widely used. Chromatography-mass spectrometry procedures are often applied to certify standard serum samples. Spectrofluorimetric, diffraction, and chromatographic techniques are common in scientific biomedical research. Nondestructive methods like nonenzymatic spectrophotometric, nonenzymatic amperometric, potentiometric, conductometric, titrimetric, and calorimetric procedures, as well as a number of enzymatic spectrophotometric procedures, in most cases, are not used in modern clinical and diagnostic practice. [ABSTRACT FROM AUTHOR]

The article presents information on a study on the impact of decreased renal function on serum holotranscobalamin (holoTC) in elderly men. The study found that serum holoTC in healthy elderly men showed same distribution as for a younger population. It is concluded that holoTC appears promising tool for cobalamin status evaluation in elderly populations.

Background: In our emergency department, we collect blood in Rapid Serum Tubes (RSTs; Becton Dickinson, Franklin Lakes, NJ), in which clotting times are reduced. We investigated the influence of RST use on cardiac troponin T (hs-cTnT) and creatine kinase-MB (CK-MB) test results, in comparison with the use of tubes featuring a separator gel containing a clotting activator (SSTs; Green-vac, Yongin, Korea). Methods: Samples from 60 patients were divided into equal aliquots and placed into RSTs and SSTs; hs-cTnT and CK-MB concentrations were determined using an autoanalyzer (Elecsys 2010) running commercial assays (Roche Diagnostics, Penzberg, Germany). Between-tube differences in CK-MB and hs-cTnT values were compared using the paired t-test, and correlations among variables were evaluated by calculation of Spearman correlation coefficients (r values). Deming regression analysis was performed and Bland-Altman plots were constructed. Results: The hs-cTnT and CK-MB test results obtained from samples placed into RSTs and SSTs did not differ (p > 0.1). The correlations between the concentrations of hs-cTnT and CK-MB in samples placed into RSTs and SSTs were good; both r values were unity (p < 0.001). Deming regression analysis yielded the equation: RST [hs-cTnT] = 0.98 SST [hs-cTnT] + 0.69 pg/ml; and RST [CK-MB] = 0.95 SST [CK-MB]-0.09 ng/ml. The biases of 1.4 pg/ml (95% CI: minus 8.1-10.7 pg/ml) for hs-cTnT levels and 0.249 ng/ml (95% CI: minus 0.682-1.681 ng/ml) for CK-MB levels assayed using either tube was acceptable. Conclusion: The hs-cTnT and CK-MB test results did not significantly differ when either tube was used. RST tube use was associated with a short clotting time; this was an advantage in an emergency laboratory setting. [ABSTRACT FROM AUTHOR]

Copyright of Turkish Journal of Biochemistry / Turk Biyokimya Dergisi is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective The purpose of this study is to evaluate the stem cell factor ( SCF) and high sensitive C reactive protein (hs- CRP) concentration in gingival crevicular fluid ( GCF) and serum of chronic periodontitis subjects with type 2 diabetes, and to evaluate the effect of nonsurgical periodontal therapy on their GCF and serum concentrations. Materials and methods A total of (age and gender matched) 22 subjects were evaluated. Pre- and post-treatment levels of SCF and hs- CRP in GCF and serum were measured and compared using enzyme linked immunosorbant assay. Clinical parameters including probing depth and clinical attachment level were also measured. Paired t-test was used to compare the before- and after-treatment levels of the two molecules. Results A highly significant difference ( P < 0.001) was found in the GCF and serum concentrations of SCF and hs- CRP before and after treatment. Conclusion Our observations indicated that short-term nonsurgical therapy resulted in a significant improvement in periodontal indices and in a marked decrease of SCF and hs- CRP serum and GCF levels. [ABSTRACT FROM AUTHOR]

In critically ill patients, mild to moderate reductions in glomerular filtration rate are not instantly followed by parallel changes in serum creatinine (SCr). The aim of this study was to identify a value of serum cystatin C (cys-C) level as a marker for monitoring renal function in critically ill pediatric patients. Creatinine clearance was used to estimate glomeruler filtration rate (eGFR). The correlation between the inverse of serum cys-C and eGFR (r = −0.70, p < 0.0001) was better than the correlation between the inverse of SCr and eGFR (r = −0.27, p = 0.008). Serum cys-C was found to be superior to SCr to predict renal impairment (area under the curve for cys-C, 0.932 and for SCr, 0.658). It can be concluded that cys-C is superior to SCr for the detection of renal impairment in critically ill children. [ABSTRACT FROM PUBLISHER]

Background: The performance of the BD Vacutainer® PST™ II Tube for testing of special chemistry analytes was evaluated in comparison to serum and heparin plasma non-gel blood collection tubes. The comparison tubes included the BD Vacutainer® Serum Plus Tube, the BD Vacutainer® Lithium Heparin Plus Tube, and the BD Vacutainer® Lithium Heparin Glass Tube. Methods: Tubes were drawn by routine venipuncture from 42 subjects according to a randomized draw order. Tubes were processed and centrifuged according to recommended handling procedures. Serum and plasma from the comparison tubes were aliquoted to secondary containers prior to analysis. Specimens were then tested for selected special chemistry analytes at two time intervals (initial time and after 24 h storage). Analytes tested included thyroid stimulating hormone, free thyroxine, total thyroxine, follicle stimulating hormone, luteinizing hormone, ferritin, cortisol, vitamin B12, folate, and testosterone. The data were collected and analyzed by analysis of variance and mean bias comparisons. Results: The performance of the BD Vacutainer® PST™ II Tube was considered to be clinically equivalent to all three comparison tubes for all assays. Test results from the BD Vacutainer® PST™ II Tube and from aliquots from the three comparison tubes at 24 h were considered to be clinically equivalent to those at initial time for all assays. Conclusions: The BD Vacutainer® PST™ II Tube provided clinically equivalent results to serum and plasma non-gel tubes and good storage stability for the assays evaluated without the need to aliquot. Clin Chem Lab Med 2009;47:358–61. [ABSTRACT FROM AUTHOR]

A sol particle homogeneous immunoassay (SPIA) is a method to measure the serum cystatin C (cysC) level as a marker of the glomerular filtration rate (GFR). Recently, formulas to convert measured cysC to GFR have been developed. A total of 154 patients (46 ± 18 years old) who had undergone renal biopsy, sodium thiosulfate clearance ( C thio) and 24-h creatinine clearance (24-hCcr) tests were subjects for the study. Their serum cysC levels were determined by SPIA. Multiple regression analysis revealed C thio and age as independent variables for serum creatinine concentration (Cr), while only C thio affected cysC. The equations using Cr or cysC showed significant correlation with C thio. Receiver-operating curve ROC analysis revealed that cysC and 24-hCcr shared comparable power to detect patients with GFR < 90 or 60 ml/min/1.73 m2 (AUC = 0.862 and 0.943 vs. AUC = 0.842 and 0.943, respectively), while Cr (AUC = 0.881) and MDRD2 (AUC = 0.888) showed slightly inferior ability to detect 60 ml/min/1.73 m2 than other parameters in the female population. The cut-off point of cysC and Cr obtained from the ROC analysis demonstrated strong power to detect patients with C thio < 90 ml/min/1.73 m2 or C thio < 60 ml/min/1.73 m2. According to CKD stages, the mean values of each equation were significantly different, like that demonstrated by 24-hCcr. SPIA could determine cysC levels that detected early renal impairment. The accuracy of cysC to detect early renal impairment may be superior to that of Cr in females, while it would be comparable to that of CG or MDRD when they are corrected by sex and age. Both cysC itself and cysC equations are effective to monitor the progress of renal impairment. The future standardization of cysC measurements and development of novel equation of cysC would contribute to the further improvement of GFR estimation in clinical practice. [ABSTRACT FROM AUTHOR]

Background and objective: Monitoring of renal function in cystic fibrosis (CF) patients is essential. The dosage regimen of amikacin is regularly modified according to the patient’s glomerular filtration rate (GFR). The aim of the study was to evaluate the use of cystatin C (CyC) for monitoring amikacin therapy along with other markers of renal tubular and glomerular function, and damage [ N-acetyl-β- d glucosaminidase (NAG), creatinine level and creatinine clearance]. Methods: We compared the GFR, estimated from the serum concentrations of creatinine (Cockcroft–Gault formula) and CyC (Grubb’s formula). Seventy-one patients (mean age 12 years; range 4–28 years) with CF were treated by intermittent intravenous infusion of amikacin. Tubular nephrotoxicity was investigated by measurement of urine NAG/urine creatinine ratio (U-NAG/U-creatinine). Concentrations of all markers were measured before starting amikacin therapy and at days 3, 5, 7, 10 and 12. Fluorescence polarization analysis, turbidimetry, enzymatic phototometric creatinine deaminase method and fluorimetry were used for determination of serum amikacin, serum CyC, creatinine and urine NAG activity. Receiver operating characteristic (ROC) analysis was performed to assess the influence of GFR estimated from serum creatinine and serum CyC for the prediction of amikacin clearance during aminoglycoside therapy. Results: Significant differences in the rate of U-NAG/U-creatinine were noted before and after treatment with amikacin ( P < 0·001). Serum creatinine levels and creatinine clearance at the end of amikacin therapy (12th day) did not show any significant differences in comparison with the levels measured before the start of therapy (0th day). At days 5, 7, 10 and 12, serum CyC levels showed a significant elevation ( P < 0·001), and CyC clearance showed a significant decrease ( P < 0·001) in comparison with the levels measured at day 0. The ratio of amikacin clearance/creatinine clearance decreased with therapy whereas the amikacin clearance/CyC and amikacin clearance/CyC clearance increased. Conclusion: We showed that the rate of U-NAG/U-creatinine is a suitable marker for monitoring tubular nephrotoxicity in CF patients. Serum creatinine and estimated creatinine clearance are modest predictors of GFR in CF patients. CyC appears to be a better marker of GFR than serum creatinine concentration or creatinine clearance in our study. Serum CyC levels and CyC clearance showed greater ability to predict amikacin clearance during therapy than creatinine clearance. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Patologia Clinica is the property of Federacion Mexicana de Patologia Clinica y de la Asociacion Latinoamericana de Patologia Clinica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The estimation of the glomerular filtration rate (GFR) is an essential part of the evaluation of patients with chronic kidney disease (CKD). Recently, serum cystatin C has been proposed as a new endogenous marker of GFR. Authors compared serum creatinine, creatinine clearance calculated from Cockcroft and Gault formula and serum cystatin C against 51CrEDTA clearance in 252 patients with CKD and GFR <90 mL/min/1.73 m2. Analysis of correlations and diagnostic accuracy (receiver operating characteristic curves) of different GFR markers indicate that serum cystatin C is a more reliable marker of GFR in patients with CKD than serum creatinine. [ABSTRACT FROM AUTHOR]

Anticoagulants are used to prevent clot formation both in vitro and in vivo. In the specific field of in vitro diagnostics, anticoagulants are commonly added to collection tubes either to maintain blood in the fluid state for hematological testing or to obtain suitable plasma for coagulation and clinical chemistry analyses. Unfortunately, no universal anticoagulant that could be used for evaluation of several laboratory parameters in a sample from a single test tube is available so far. Ethylenediamine tetraacetic acid (EDTA) is a polyprotic acid containing four carboxylic acid groups and two amine groups with lone-pair electrons that chelate calcium and several other metal ions. Calcium is necessary for a wide range of enzyme reactions of the coagulation cascade and its removal irreversibly prevents blood clotting within the collection tube. Historically, EDTA has been recommended as the anticoagulant of choice for hematological testing because it allows the best preservation of cellular components and morphology of blood cells. The remarkable expansion in laboratory test volume and complexity over recent decades has amplified the potential spectrum of applications for this anticoagulant, which can be used to stabilize blood for a variety of traditional and innovative tests. Specific data on the behavior of EDTA as an anticoagulant in hematology, including possible pitfalls, are presented. The use of EDTA for measuring cytokines, protein and peptides, and cardiac markers is described, with an outline of the protection of labile molecules provided by this anticoagulant. The use of EDTA in proteomics and in general clinical chemistry is also described in comparison with other anticoagulants and with serum samples. Finally, the possible uses of alternative anticoagulants instead of EDTA and the potential use of a universal anticoagulant are illustrated. Clin Chem Lab Med 2007;45:565–76. [ABSTRACT FROM AUTHOR]

In this study, we aimed to compare Cystatin C (Cys C) with other traditional glomerular filtration rate (GFR) markers and to evaluate its superiority over them in detecting early renal involvement in patients with primary hypertension. Fifty-one primary hypertensive patients and 29 healthy control subjects, who were similar in terms of age and gender, were included in the study. In all subjects serum levels of Cys C, beta-2 microglobulin, serum creatinine (SCr), uric acid, BUN, albumin; 24 h urinary levels of protein (U pro ), albumin (U alb ) and creatinine were measured. The GFR was calculated according to Creatinine Clearance (CrCl), Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas. The MDRD was used as the reference method. A GFR 2 was considered as the lower cut-off limit. Mean levels of the serum parameters were found to be significantly higher in the patient group than they were in the control group ( p [ABSTRACT FROM AUTHOR]

Conflicting data in the literature concern possible differences in the immunochemical measurement of cardiac troponins, either in plasma or in serum. In order to address this specific point, 96 serum and heparin- plasma pairs were obtained for cardiac marker measurement [cardiac troponin I (cTnT); myoglobin (Myo) and creatine kinase-MB isoenzyme (CK-MB)]; 29 additional "common" analytes were measured in 77 such samples. The cardiac markers were measured by electrochemiluminescence (Elecsys 2010, Roche); the other analytes by established automated methods (Modular, Roche). Mean plasma/serum ratios for cTnT (0.95), creatine kinase-MB (1.01) and myoglobin (0.99) were comparable with those of the 29 common analytes (interval of means 0.83-1.05). The distribution of the plasma-serum differences also showed similarities between cardiac markers and other analytes. A few outlier plasma-serum differences (3-5%) were measured for both categories of analytes. Addition of heparin to serum (51 samples) caused decreased cTnT (mean ratio 0.92). In 3 of 51 such samples the cTnT decrease was more marked, but in a second sample from the same subjects (1 week later) such a prominent, heparin-induced loss of cTnT no longer appeared. In conclusion, plasma-serum differences in immuno-reactive cTnT compare with those observed for other analytes. In occasional heparin-plasma samples immunochemical measurement of cTnT may give exceptionally low values. However, in our sample group of 96 patients (cTnT lower or higher than the cut-off in, respectively, 24 and 72 patients), no misclassification occurred if plasma instead of serum cTnT values were considered. [ABSTRACT FROM AUTHOR]

Glomerular filtration rate (GFR) and urine and serum concentrations of cystatin C and creatinine were measured in 40 boys and 42 girls. The fractional excretion of cystatin C (FE Cyst C) increased in proportion to the decrease in GFR. Since serum creatinine concentration (S-Creatinine) in the numerator of the fractional excretion equation and serum cystatin C concentration (S-Cystatin C) in the denominator have similar numerical values, they cancel out. The result is an equation in which the FE Cyst C is equal to the ratio of urinary cystatin C to urinary creatinine (u[cystatin-C/Cr]). The ratio of u[cystatin Cl Cr] was compared with GFR. Using a receiving operating characteristic (ROC) plot, the data showed that a ratio of u[cystatin C/Cr]*I00 that is ≥0.100 has a sensitivity of 90.0% for identification of children with GFR ≤60 ml/min per 1.73 m². The false-positive rate is 16.1%. The u[cystatin C/Cr] ratio is a reliable screening tool for detecting decreased GFR that does not require a serum sample. [ABSTRACT FROM AUTHOR]

Background: Reliability of cardiac troponin-I assays under real-time conditions has not been previously well studied. Most large published cTnI trials have utilized protocols which required the freezing of serum (or plasma) for delayed batch cTnI analysis. We sought to correlate the presence of the acute ischemic coronary syndrome (AICS) to troponin-I values obtained in real-time by three random-mode analyzer immunoassay systems: the Beckman ACCESS (BA), the Bayer ACS:180 (CC) and the Abbott AxSYM (AX). Methods: This was an observational prospective study at a university tertiary referral center. Serum from a convenience sampling of telemetry patients was analyzed in real-time for troponin-I by either the BA-CC (Arm-1) or BA-AX (Arm-2) assay pairs. Presence of the AICS was determined retrospectively and then correlated with troponin-I results. Results: 100 patients were enrolled in Arm-1 (38 with AICS) and 94 in Arm-2 (48 with AICS). The BA system produced 51% false positives in Arm-1, 44% in Arm-2, with negative predictive values of 92% and 100% respectively. In Arm-1, the BA and the CC assays had sensitivities of 97% and 63% and specificities of 18% and 87%. In Arm-2, the BA and the AX assays had sensitivities of 100% and 83% and specificities of 11% and 78%. Conclusions: In real-time analysis, the performance of the AxSYM and ACS:180 assay systems produced more accurate troponin-I results than the ACCESS system. [ABSTRACT FROM AUTHOR]

Background: Conventional estimates of glomerular dysfunction, including serum creatinine and creatinine clearance, are inadequate in older people. In this study we have compared the diagnostic accuracy of a novel test of kidney disease, cystatin C, against these markers in older patients with a range of renal function. Methods: Fifty-three patients (mean age 79.6 years, range 69-92 years) with a variety of medical diagnoses were recruited via outpatient clinics. Exclusion criteria included active rheumatoid disease, known current malignancy, renal replacement therapy/renal transplantation and cognitive impairment. 51Cr-EDTA was used as the reference method against which the other markers of glomerular filtration rate were compared using regression analyses. Results: The best fit with glomerular filtration rate was given by Cockcroft and Gault calculated clearance (R2 = 0.83), followed by serum cystatin C (R2 = 0.79), serum creatinine (R2 = 0.76) and creatinine clearance (R2 = 0.73). The accuracy for glomerular filtration rate prediction was poor for all markers. Serum cystatin C detected nearly all patients with mild renal impairment whereas serum creatinine only detected half of these cases. Regression modelling predicted that the upper limit of normal for serum cystatin C would be exceeded as glomerular filtration rate fell below 64 mL/min/1.73 m2, compared with 44 mL/min/1.73 m2 for serum creatinine. Conclusion: Serum cystatin C is a simple and sensitive screening test for kidney dysfunction in older people. [ABSTRACT FROM AUTHOR]

AbstractBackground: Serum creatinine is the most common endogenous marker used to estimate the glomerular filtration rate (GFR). However, creatinine depends considerably on muscle mass, and its tubular secretion increases, especially in chronic renal failure. Cystatin C is a 13-kD protease inhibitor which is produced by all nucleated cells and is independent of muscle mass and sex. Cystatin C is eliminated by glomerular filtration and metabolized by proximal tubular cells. Its measurement has been proposed as an alternative and more sensitive marker of GFR than creatinine in patients with slight to moderately decreased GFR. Methods: We investigated serum cystatin C levels in comparison with creatinine as a single measurement for estimation of GFR in 173 patients after renal transplantation. GFR was calculated as creatinine clearance according to standard equations. Results: Serum creatinine correlated well with cystatin C (r = 0.84; p < 0.0001). No significant differences were obtained for the comparison of the linear correlation of 1/creatinine with creatinine clearance (r = 0.77; p < 0.0001) and for the linear correlation of 1/cystatin C with creatinine clearance (r = 0.73; p < 0.0001). However, we found a significant advantage of cystatin C in detecting a clinical relevant reduction of kidney function (GFR <70 ml/min; p = 0.0047, McNemar test). Conclusion: Cystatin C is an alternative marker for the assessment of GFR in renal allograft recipients that may be superior to creatinine.Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

There is an increasing demand for the results of cardiac markers (troponin I or T, creatine kinase MB mass and myoglobin) to be made available promptly after sample-taking. In order to shorten the turnaround time, the possibility of using EDTA- or heparin-plasma instead of serum was investigated. The study population comprised 391 patients with acute chest pain. Four different instruments and systems routinely used in Finland giving quantitative results were studied for the assays of creatine kinase isoenzyme MB mass, myoglobin, and troponin I or troponin T. In addition to serum samples, heparin-plasma seems to be useful for all three assays using the Access and Immulite systems, while EDTA-plasma seems to be useful for all three assays with the Access and Elecsys systems. For the AxSYM assays, serum samples seem to be the best alternative. In conclusion, it is possible to use a single EDTA- or heparin-plasma sample for Access, Elecsys and Immulite analysers, and thereby to shorten the turnaround time. In this way the quantitative analyses from plasma can be performed 30 min after taking the sample. [ABSTRACT FROM AUTHOR]

Altered renal function is an essential component of the pathophysiological process in preeclampsia. The kidneys play a significant part in the turnover of most low molecular weight substances such as creatinine, urate and cystatin C. The present work was undertaken to investigate if the serum levels of these components are altered in characteristic ways in preeclampsia, and can be used to assist in the diagnosis of this condition. The serum levels were therefore determined in samples from 100 healthy women at term as well as in 45 samples of patients with preeclampsia (diastolic blood pressure > 90 mmHg; urinary albumin excretion > 300 mg L[sup -1]). The levels of all three components were significantly higher in samples from preeclamptic patients with the mean ± SD being 1.55 ± 0.29 vs. 1.05 ± 0.19 mg L[sup -1] for cystatin C, 70 [sup ±] 23 vs. 56 [sup ± ]9.7 mumol L[sup -1] for creatinine, and 413 ± 128 vs. 305 ± 61 mumol L[sup -1] for urate. Receiver operating characteristic analysis demonstrated that the serum level of cystatin C had a superior diagnostic accuracy for preeclampsia compared to those of serum urate and creatinine and that the diagnostic accuracy of serum urate was better than that of serum creatinine. [ABSTRACT FROM AUTHOR]

Background: Cystatin C (MW 13 kDa) serum concentration reflects glomerular filtration rate better than creatinine. Like other low-molecular weight proteins it is not eliminated by dialysis. Still, cystatin C serum concentrations do not rise progressively in end-stage renal failure and rarely exceed 10 mg/L (i.e. 8 times the upper limit of normal). Objective: To study cystatin C kinetics in a rat model of end-stage renal failure. METHODS: Sequential bilateral nephrectomy was performed seven days apart in 13 male Sprague-Dawley rats as described by Levine and Saltzman. Serum cystatin C (Cystatin C PET-kit, DAKO), creatinine and total protein were measured in daily intervals after the second nephrectomy. Linearity of the anti-human cystatin C assay for rat cystatin C was tested using dilutions of uremic rat serum. Rats were sacrificed for signs of severe uremia on days 10 (n = 5), 11 (n = 4) and 12 (n = 5). RESULTS: At baseline, mean (± SE) cystatin C was 1.59 ± 0.041 mg/L, creatinine 19.6 ± 1.2 μmol/L. Following bilateral nephrectomy, cystatin C immediately rose to 3.82 ± 0.15 mg/L, creatinine to 312 ± 20 μmol/L. During the following days, cystatin C concentration stabilized to 4 mg/L approximately whereas creatinine continued to rise to 822 ± 185 μmol/L on day 12. Correction for the decrease in serum total protein concentration from 48.9 ± 2.3 g/L to 37.4 ± 3.6 g/L did not alter these results. CONCLUSION: The kinetics of cystatin C and creatinine in this rat model of end-stage renal failure are in accordance withh uman data suggesting a change in cystatin C production or extra-renal elimination in severe chronic uremia. [ABSTRACT FROM AUTHOR]

Chromogranin A (CGA) is a low MW (49,000) acidic hydrophilic protein. It is synthesized in the chromaffm granules of the neuroendocrine cells, and has been found circulating in the blood of healthy subjects. The aim of this study was to assess the relationship between serum levels of CGA and renal function. One hundred two renal patients (45 M and 57 F; age 14–76 years, mean 52) participated in the study. Glomerular filtration rate (GFR) was measured by the bladder cumulative method, using 99mTc-DTPA as a tracer. Blood CGA was determined by RIA. Plasma creatinine, β2microglobulin (β2m) and tumor associated trypsin inhibitor (TATI) were also determined. The reduction in renal function was associated with an increase in all of the above studied parameters. In patients with advanced renal failure (GFR < 20 mL/min) CGA levels increased by 22-fold as compared to the patients with normal renal function (GFR > 100 mL/min). The other studied parameters were also increased but to a lesser degree, e.g., TATI 14-, β2m 8- and creatinine 5-fold. The results of this study demonstrate that renal handling of the CGA is similar to other low MW proteins, and it accumulates in the blood in renal failure. [ABSTRACT FROM AUTHOR]

To date, little evidence is available to define the role of cystatin C in patients with renal transplants. Thus, to assess, whether cystatin C (CysC) provides better information on renal function than other markers, CysC, creatinine clearance (CrCl), serum creatinine (SCr), β2-microglobulin (β2-M), and 125I-Iothalamate clearance were determined in 30 patients. Correlation and ROC curves were obtained and characteristics like sensitivityand specificity were calculated. Further, to evaluate the usefulness of these markers for monitoring, intraindividual coefficients of variation for CysC and SCr measurements were compared in 85 renal transplant patients. CysC correlated best with GFR, whereas SCr, CrCl and β2-M all had lower correlation coefficients. CysC was superior to SCr, even when renal function equations of were used. The diagnostic accuracy of CysC was significantly better than SCr, but did not differ significantly from CrCl and β2-M. Together, our data show that in patients with renal transplants, CysC has a similar diagnostic value as CrCl. However, it is superior to determinations of SCr. The intraindividual variation of CysC is significantly greater than that of SCr. This might be due to better ability of CysC to reffect temporary changes especially in mildly impaired GFR, most critical for early detection of rejection and other function impairment. In conclusion, CysC allows for easy and accurate assessment of renal function (GFR) in steady state renal transplant patients and is clearly superior to the commonly used serum creatinine. [ABSTRACT FROM AUTHOR]

Serum cystatin C measurement has been previously shown by ourselves and others to be a better indicator of changes in glomerular filtration rate (GFR) than serum creatinine. However, the available literature on reference values for cystatin C concentration remains surprisingly sparse; we thus set out to determine an adult reference range. Blood was taken from 309 healthy blood donors and creatinine and cystatin C concentrations were measured using commercially available automated methodologies. In addition, predicted creatinine clearances were calculated using the Cockcroft and Gault formula. The 95% reference intervals for creatinine, predicted creatinine clearance and cystatin C for all blood donors, regardless of gender, were 68-118 µmol/L, 58-120 ml/min/1·73 m 2 and 0·51-0·98 mg/L, respectively. For women, the intervals were 68-98 µmol/L, 60-119 ml/min/1·73 m 2 and 0·49-0·94 mg/ L; for men, they were 78-123 µmol/L, 57-122 ml/min/1·73 m 2 and 0·56-0·98 mg/L. The mean 95% reference interval for cystatin C in all donors under 50 years of age was 0·53-0·92 mg/L; for those over 50 years of age it was 0·58-1·02 mg/L. The small difference between male and female ranges meant that a single reference range for cystatin C could be established for all adults under 50 years of age without adjustment for body surface area. Serum cystatin C measurement offers a simpler and more sensitive screening test than serum creatinine for early changes in GFR. [ABSTRACT FROM AUTHOR]

In an effort to increase our knowledge of the optimal use of serum cystatin C and creatinine as glomerular filtration rate (GFR) markers, these variables, as well as lean tissue mass and GFR, were determined in a population of 42 healthy young adults (men and women with normal GFR). Dual­energy X­ray absorptiometry and measurement of the plasma clearance of iohexol were used to measure lean tissue mass and GFR, respectively. Serum creatinine was significantly correlated to lean tissue mass (r=0.65; p<0.0001) but not to GFR (1/creatinine vs. GFR: r=0.11; p=0.106). In contrast, serum cystatin C correlated with GFR (1/cystatin C vs. GFR: r=0.32; p=0.0387), especially in men (1/cystatin C vs. GFR: r=0.64; p=0.0055), but not to lean tissue mass. These results might explain previous observations that serum cystatin C seems to be a better marker for GFR than serum creatinine, particularly for individuals with small to moderate decreases in GFR. However, the results also show that the serum concentrations of both creatinine and cystatin C are determined not only by GFR, but also by other factors. Since these additional factors differ for cystatin C and creatinine, it seems justified to use serum creatinine and cystatin C in conjunction to estimate GFR, at least until it is known in what situations serum creatinine or cystatin C is the preferable marker. [ABSTRACT FROM AUTHOR]

The IFCC Working Group for the Standardisation of Cystatin C (WG-SCC), in collaboration with the Institute for Reference Materials and Measurements (IRMM), announces the availability of the new certified reference material ERM-DA471/IFCC. The material was characterised using a pure protein primary reference preparation (PRP) as calibrant. The PRP was prepared from recombinant cystatin C, and its concentration measured using dry mass determination. The characterisation of ERM-DA471/IFCC was performed by particle enhanced immuno-nephelometry, particle enhanced immuno-turbidimetry, and enzyme amplified single radial immuno-diffusion. The certified cystatin C mass concentration in ERM-DA471/IFCC, if reconstituted according to the specified procedure, is 5.48 mg/L, the expanded uncertainty ( k=2) being 0.15 mg/L. Clin Chem Lab Med 2010;48:1619-21. [ABSTRACT FROM AUTHOR]

No Abstract available [ABSTRACT FROM AUTHOR]

Background: We have observed discrepancies between C-reactive protein (CRP) measured in serum prepared from a serum separator tube (SST) and that obtained from a plain tube, when using the Vitros CRP assay. Our study aimed at elucidating the cause of these discrepancies. Methods: Eighty-seven specimens from hospitalized patients with various types of inflammatory disease were analysed using a fixed-point immuno-rate method on a Vitros CRP slide. The serum was prepared simultaneously in both vacuum and SSTs. We also performed mixing tests by adding 47 samples of serum prepared from plain tubes to SSTs and incubating for 15 min before CRP analysis. Results: Lower values of CRP were found in serum prepared from plain tubes than in serum from SSTs. Addition of serum prepared from plain tubes to SSTs and incubating for 15 min increased the CRP values significantly. The ratio of CRP measured in serum prepared from plain tubes and from SSTs did not differ significantly from the ratio obtained when serum was prepared in a plain tube then added to an SST. Discussion: We propose that SSTs can adsorb some macromolocules that form complexes with CRP. The addition of SST gel to serum results in the release of CRP molecules from these complexes, which enhances the antigen-antibody reaction on the Vitros CRP slide and increases the measured CRP concentrations. [ABSTRACT FROM AUTHOR]

Determination of C-reactive protein (CRP) and high-sensitivity CRP (hs-CRP), markers of systemic inflammation and atherosclerosis risk, usually requires serum samples, while heparin plasma samples are routinely collected for routine chemistry. This study evaluates the use of heparin plasma samples for hs-CRP and CRP determinations using immunoturbidimetric methods on an Olympus system. As a result, analytical performance, including linearity, imprecision values, and determination from 185 clinical samples, are not affected by the type of sampling, validating the use of heparin plasma samples for CRP and hs-CRP determination with Olympus reagents. [ABSTRACT FROM AUTHOR]