Calibration of the Siemens Cystatin C Immunoassay Has Changed over Time

Clinical ChemistryUppsala UniversityUppsala, Sweden.
Clinical Chemistry (Impact Factor: 7.77). 03/2011; 57(5):777-8. DOI: 10.1373/clinchem.2010.159848
Source: PubMed
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    ABSTRACT: The Cockcroft-Gault equation for estimating glomerular filtration rate has been learnt by every generation of medical students over the decades. Since the publication of the Modification of Diet in Renal Disease (MDRD) study equation in 1999, however, the supremacy of the Cockcroft-Gault equation has been relentlessly disputed. More recently, the Chronic Kidney Disease Epidemiology (CKD-EPI) consortium has proposed a group of novel equations for estimating glomerular filtration rate (GFR). The MDRD and CKD-EPI equations were developed following a rigorous process, are expressed in a way in which they can be used with standardized biomarkers of GFR (serum creatinine and/or serum cystatin C) and have been evaluated in different populations of patients. Today, the MDRD Study equation and the CKD-EPI equation based on serum creatinine level have supplanted the Cockcroft-Gault equation. In many regards, these equations are superior to the Cockcroft-Gault equation and are now specifically recommended by international guidelines. With their generalized use, however, it has become apparent that those equations are not infallible and that they fail to provide an accurate estimate of GFR in certain situations frequently encountered in clinical practice. After describing the processes that led to the development of the new GFR-estimating equations, this Review discusses the clinical situations in which the applicability of these equations is questioned.
    Nature Reviews Nephrology 07/2013; 9(9). DOI:10.1038/nrneph.2013.143 · 8.37 Impact Factor
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    ABSTRACT: Serum creatinine (SCr) is the main variable for estimating glomerular filtration rate (GFR). Due to inter-assay differences, the prevalence of chronic kidney disease (CKD) varies according to the assay used, and calibration standardization is necessary. For SCr, isotope dilution mass spectrometry (IDMS) is the gold standard. Systematic differences are observed between Jaffe and enzymatic methods. Manufacturers subtract 0.30 mg/dl from Jaffe results to match enzymatic results ('compensated Jaffe method'). The analytical performance of enzymatic methods is superior to that of Jaffe methods. In the original Modification of Diet in Renal Disease (MDRD) equation, SCr was measured by a Jaffe Beckman assay, which was later recalibrated. A limitation of this equation was an underestimation of GFR in the high range. The Chronic Kidney Disease Epidemiology (CKD-EPI) consortium proposed an equation using calibrated and IDMS traceable SCr. The gain in performance was due to improving the bias whereas the precision was comparable. The CKD-EPI equation performs better at high GFR levels (GFR >60 ml/min/1.73 m(2)). Analytical limitations have led to the recommendation to give a grade (>60 ml/min/1.73 m(2)) rather than an absolute value with the MDRD equation. By using both enzymatic and calibrated methods, this cutoff-grade could be increased to 90 ml/min/1.73 m(2) (with MDRD) and 120 ml/min/1.73 m(2) (with CKD-EPI). The superiority of the CKD-EPI equation over MDRD is analytical, but the precision gain is limited. IDMS traceable enzymatic methods have been used in the development of the Lund-Malmö (in CKD populations) and Berlin Initiative Study equations (in the elderly). The analytical errors for cystatin C are grossly comparable to issues found with SCr. Standardization is available since 2011. A reference method for cystatin C is still lacking. Equations based on standardized cystatin C or cystatin C and creatinine have been proposed. The better performance of these equations (especially the combined CKD-EPI equation) has been demonstrated.
    Journal of nephrology 04/2014; 27(5). DOI:10.1007/s40620-014-0087-7 · 2.00 Impact Factor
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    ABSTRACT: Objective: In reliable clinical laboratory practice, to use test results for the maximum benefit of patients, the new method in a laboratory should be validated. In this study our purpose is to evaluate performance characteristics of cystatin C immunoturbidimetric method in Roche Cobas Integra 800 analyser, and compare this method with immunonephelometric method in Dade Behring BNII analyser. Methods: Precision, linearity, recovery, interference experiments in Roche Cobas Integra 800 analyser and method comparison experiments were performed for cystatin C. Results: For Roche Cobas Integra 800 instrument, low and high concentrations for withinrun and day to day CV values were 3.97%, 1.32% and 7.24%, 4.16% respectively. In linearity experiment, regression graph equation was found to be y = 0.9817x - 0.0149 and r(2) = 0.99. In recovery experiment, % recovery was found to be 81. In hemolysis interference experiment, interference was detected for the hemoglobin concetrations above 200 mg/dL, Method comparison experiment was performed by analyzing 100 patients serum in both Dade Behring BNII nephelometry and Roche Cobas Integra 800 analyser. Correlation factor was r(2) = 0.95, Deming regression equation was y = 0,98x + 0,22. Conclusion: It was found for turbidimetric method, CV values were higher, % recovery was lower and hemolysis interference was detected at lower concentrations than what was stated in package insert of cystatin C kits. However, Deming regression results indicated turbidimetric and nephelometric methods were compatible.
    Türk Biyokimya Dergisi / Turkish Journal of Biochemistry 01/2013; 38(3):239-242. DOI:10.5505/tjb.2013.81300 · 0.17 Impact Factor


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Feb 2, 2015