Estimated GFR in stable older kidney transplant recipients - are present algorithms valid? A national cross-sectional cohort study.

Several equations have been developed for estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease (CKD), but none were developed based on data from elderly kidney transplant recipients (KTR). The primary aim of this study was to evaluate different creatinine-based equations in stable elderly KTR. A national cross-sectional study was performed using data from 263 consecutive kidney transplant recipients 60 years or older who performed a routine GFR measurement one year after engraftment. GFR was measured by iohexol clearance calculation based on two samples. eGFR was calculated from a range of different creatinine-based equations using information obtained at the time of GFR measurement. Bias, precision, and accuracy were evaluated for each equation. All equations apart from Nankivell had accuracy (P30) > 80%. The BIS1, FAS, LMRCR, and Cockcroft & Gault equations in recipients older than 70 years and the FAS, LMRCR, and MDRD in recipients 60-69 years old had nonsignificant bias. The CKD-EPI had significant bias in both groups. If one should choose a single equation for follow-up of individual CKD progression in all recipients 60 years, the FAS or LMRCR equations are probably the best alternatives.