Comparison of MDRD equations and the old equations CKD-EPI against new equations CKD-EPI in patients with kidney transplantation when used 51Cr-EDTA to measure glomerular filtration

Abstract

BackgroundWhen estimating the glomerular filtration rate (GFR) in kidney transplant patients, significant differences have been found between MDRD and the 2009 CKD-EPI equations, and reference techniques. ObjectiveTo analyse and compare the performance of MDRD and the 2009 and 2012 CKD-EPI equations against 51Cr-EDTA plasma clearance in measuring GFR in 270 kidney transplant patients after one year. ResultsThe mean measured GFR was 43.0 ± 11.4 (18.2–79.4) ml/min/1.73 m2, with creatine levels of 1.42 ± 0.46 (0.60–4.33) mg/dl and cystatin C levels of 1.45 ± 0.53 (0.42–3.48) mg/l. This correlated moderately with creatinine (r=–0.61, p < 0.001) and cystatin C (r=–0.52, p < 0.001). Using linear regression techniques, it was found that creatinine, cystatin C, gender and age only explained 52% of GFR total variance. All equations overestimated GFR, with a mean bias of +11.1 ml/min/1.73 m2 for MDRD, +16.4 ml/min/1.73 m2 for 2009-CKD-EPI, +15 ml/min/1.73 m2 for CKD-EPI with cystatin C and +14.1 ml/min/1.73 m2 for 2012-CKD-EPI with creatinine and cystatin C. eGFR by MDRD and the 2009 CKD-EPI equation correlated better with 51Cr-EDTA than CKD-EPI with creatinine and/or cystatin C. The overestimations were negatively correlated with creatinine and cystatin C levels, most significantly for CKD-EPI with creatinine and/or cystatin C when GFR was greater than 60 ml/min/1.73 m2. ConclusionsThe 2012 CKD-EPI equations with creatinine and/or cystatin C significantly overestimate GFR in stage 1 and 2 chronic kidney disease. The MDRD equation is therefore recommended in these cases. The reference method used to measure GFR seems to heavily influence the bias of the equations.