Resumo

HILDERINK, Judith M et al. Biological Variation of Creatinine, Cystatin C, and Estimated Glomerular Filtration Rate over 24 hours. Acta bioquím. clín. latinoam. [online]. 2018, vol.52, n.4, pp.489-500. ISSN 0325-2957.

Background: Estimated glomerular filtration rate (eGFR) is widely used in clinical practice. This study assessed the within-subject biological variation (CVI) of different eGFR equations in people with chronic kidney disease (CKD) and people without CKD. The aims of this study were (a) to determine the 24-h biological variation profiles of creatinine, cystatin C, and eGFR and (b) to determine whether CVI of creatinine, cystatin C, and eGFR changes on deterioration of glomerular filtration. Methods: Hourly blood samples were analyzed from 37 individuals (17 without CKD, 20 with CKD) during 24 h. Creatinine (enzymatic method) and cystatin C were measured using a Cobas 8000 (Roche Diagnostics). eGFR was estimated using the Modification of Diet in Renal Disease and the Chronic Kidney Disease Epidemiology Collaboration based on creatinine and/or cystatin C. Plasma samples were stored at -80 °C before analysis. Outlier and homogeneity analyses were checked before performing a nested ANOVA to determine biological variation. Results: CVI of creatinine was higher in people without CKD than in those with CKD (6.4% vs. 2.5%) owing primarily to the more profound effect of meat consumption on creatinine variability in individuals with lower baseline creatinine concentrations. Unlike creatinine, cystatin C concentrations were unaffected by meat consumption. Cystatin C showed some diurnal rhythmic variation and less in people with CKD. Reference change values (RCVs) of all eGFR equations were within 13% to 20% in both study groups. Conclusions: Despite differences in CVI of creatinine, the CVI and RCV of the eGFR equations were relatively similar for people with or without CKD.

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