Calibration of the Siemens Cystatin C Immunoassay Has Changed over Time

Clinical ChemistryUppsala UniversityUppsala, Sweden.
Clinical Chemistry (Impact Factor: 7.91). 03/2011; 57(5):777-8. DOI: 10.1373/clinchem.2010.159848
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Available from: Anders Larsson, Feb 02, 2015
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    • "As the measured daily urinary creatinine excretion was not available in our patients, CPR was calculated as previously described (25,26), estimating GFR from cystatin C by means of the equation of Hoek et al. (21). Although this equation was developed in 2003 (21), and calibration of the PENIA cystatin C assay may have changed over time (32), the Hoek formula has recently been favourably evaluated by different authors (33–36). "
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    ABSTRACT: Background. It has recently been reported that patient selection has a strong impact on the agreement between glomerular filtration rate (GFR) estimates from serum cystatin C and creatinine. The aim of our study was to evaluate the effect of creatinine production rate (CPR) on this subject. Material and methods. GFR was estimated from serum cystatin C and from creatinine using the 4- and 6-variable Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in 50 healthy subjects, 43 patients with renal failure, 794 kidney and 104 liver transplant recipients, 61 patients with heart failure, 59 patients with biliary obstruction, and 113 critically ill patients. Results. In the 295 patients with impaired CPR (< 900 mg/24 h/1.73 m2), discordances of more than 40% between GFRMDRD4 and GFRcystatinC were observed in 38% of cases, between GFRMDRD6 and GFRcystatinC in 22%, and between GFRCKD-EPI and GFRcystatinC in 27% (in all cases due to GFR overestimation from creatinine). In the 929 patients with maintained CPR (> 900 mg/24 h/1.73 m2), greater discordances than 40% between GFRMDRD4 and GFRcystatinC were observed in 8% of cases, between GFRMDRD6 and GFRcystatinC in 9%, and between GFRCKD-EPI and GFRcystatinC in 7% (in the major part of cases due to GFR overestimation from cystatin C). Conclusion. The main source of differences of more than 40% between GFR estimates from serum creatinine and cystatin C is a GFR overestimation in patients with low CPR and GFR underestimation in patients with high CPR by the creatinine-derived equations.
    Full-text · Article · Jul 2012 · Upsala journal of medical sciences
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    • "However, it is notably, that the proportion with no signs of renal damage is highest in the group with no CKD based on the CysC-CKD definition. Therefore, further studies should evaluate the CysC-eGFR equations in large diverse populations and further standardization of assays is needed; especially with the Siemens Cystatin C method calibration has changed during the last five years; a downward shift in calibrator had occurred between 2006 and 2009 [32]. This has to be considered if results obtained from older lots are compared to the current study. "
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    ABSTRACT: Background Chronic kidney disease (CKD) represents a global public health problem. Few data exist in the elderly. The objective of the current study is to estimate the prevalence of CKD by means of various established and new equations and to identify the main determinants of CKD in elderly. Methods The ActiFE Ulm (Activity and Function in the Elderly in Ulm) study is a population-based cohort study in people of 65 years and older. Kidney function was assessed by means of estimated glomerular filtration rate (eGFR) based on two creatinine- (Cr-; MDRD, CKD-EPI) and one cystatin C - (CysC-) based method. The relationship between various potential risk factors and CKD was quantified using unconditional logistic regression. Results A total of 1471 subjects were in the final analysis (mean age 75.6 years, SD 6.56). Overall, prevalence of CKD (eGFR < 60 mL/min/1.73 m2) was 34.3% by MDRD, 33.0% by CKD-EPI, and 14.6% by the CysC-based eGFR. All eGFRs showed statistically significant correlations with C-reactive protein, uric acid, as well as with lipid values. In multivariable analysis age was clearly related to prevalence of CKD and the risks were highest with the CysC-based equation. Females had a higher risk for CKD stages 3–5 with MDRD (OR 1.63; 95% CI: 1.23–2.16) whereas the OR was 1.23 (95% CI 0.92–1.65) with the CKD-Epi and OR = 0.89 (95% CI 0.58–1.34) with the CysC-based equation after multivariable adjustment. Although the cystatin C based definition of CKD resulted in a lower prevalence compared to the creatinine based ones, other measures of renal damage such as albuminuria were more prevalent in those defined by CysC-eGFR. Conclusions Prevalence of CKD is very variable based on the used estimating equation. More work is needed to evaluate the various estimating equations especially in elderly before we are able to assess the practical consequences of the observed differences.
    Full-text · Article · May 2012 · BMC Public Health
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    • "This might have influenced our results. A recent study however, has shown that when using the Gentian method the cystatin C levels were stable when comparing blood samples over four years of time [22]. "
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    ABSTRACT: Sedentary lifestyle is associated with coronary artery disease but even shorter periods of physical inactivity may increase cardiovascular risk. Cystatin C is independently associated with cardiovascular disease and our objective was to investigate the relation between this novel biomarker and standardized bed rest. Research of immobilization physiology in humans is challenging because good biological models are in short supply. From the Women International Space simulation for Exploration study (WISE) we studied markers of atherosclerosis and kidney function, including cystatin C, in a standardized bed rest study on healthy volunteers. Fifteen healthy female volunteers participated in a 20-day ambulatory control period followed by 60 days of bed rest in head-down tilt position (-6°) 24 h a day, finalized by 20 days of recovery. The subjects were randomized into two groups during bed rest: a control group (n = 8) that remained physically inactive and an exercise group (n = 7) that participated in both supine resistance and aerobic exercise training. Compared to baseline values there was a statistically significant increase in cystatin C in both groups after bed rest (P < 0.001). Glomerular filtration rate (GFR), calculated by both cystatin C and Cockcroft-Gault equation, decreased after bed rest while there were no differences in creatinine or creatine kinase levels. CRP did not change during bed rest in the exercise group, but there was an increase of CRP in the control group during recovery compared to both the baseline and the bed rest periods. The apo-B/apo-Ai ratio increased during bed rest and decreased again in the recovery period. Subjects experienced a small but statistically significant reduction in weight during bed rest and compared to baseline weights remained lower at day 8 of recovery. During and following prolonged standardized bed rest the concentrations of several clinically relevant cardiovascular risk markers change.
    Full-text · Article · Dec 2011 · BMC Physiology
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