Comparison of glomerular filtration rate estimating equations derived from creatinine and cystatin C: validation in the Age, Gene/Environment Susceptibility-Reykjavik elderly cohort.

To access publisher's full text version of this article click on the hyperlink belowValidation studies comparing glomerular filtration rate (GFR) equations based on standardized creatinine and cystatin C assays in the elderly are needed. The Icelandic Age, Gene/Environment Susceptibility-Kidney cohort was used to compare two pairs of recently developed GFR equations, the revised Lund-Malmö creatinine equation (LMRCr) and the arithmetic mean of the LMRCr and Caucasian, Asian, Paediatric and Adult cystatin C equations (MEANLMR+CAPA), as well as the Full Age Spectrum creatinine equation (FASCr) and its combination with cystatin C (FASCr+Cys), with the corresponding pair of Chronic Kidney Disease Epidemiology Collaboration equations (CKD-EPICr and CKD-EPICr+Cys). A total of 805 individuals, 74-93 years of age, underwent measurement of GFR (mGFR) using plasma clearance of iohexol. Four metrics were used to compare the performance of the GFR equations: bias, precision, accuracy [including the percentage of participants with estimated GFR (eGFR) within 30% of mGFR (P30)] and the ability to detect mGFR 90%. LMRCr and FASCr yielded significantly higher precision and P30 than CKD-EPICr, while bias was significantly worse. LMRCr, FASCr and CKD-EPICr showed similar ability to detect mGFR