Pre-donation assessment of cystatin C to improve prediction of pre- and post-donation GFR in potential living kidney donors.

Background: Accurate estimation of glomerular filtration rate (GFR) is crucial in living kidney donation. While most estimated GFR (eGFR) equations are based on plasma creatinine, its levels are strongly influenced by muscle mass. Application of cystatin C (cysC)-based estimates before donation may improve both estimation of current GFR and prediction of post-donation GFR.

Methods: We assessed the performance of Chronic Kidney Disease Epidemiology Collaboration equations based on creatinine (eGFRcreat-2009, eGFRcreat-2021), cysC (eGFRCysC-2012) or both (eGFRcombined-2012, eGFRcombined-2021) for estimating pre- and post-donation (mGFR) GFR in 486 living kidney donors. We subsequently focused on a subgroup of individuals with high/low muscle mass (25% highest/lowest 24-hour urinary creatinine excretion, sex stratified and height indexed).

Results: Pre-donation eGFRcombined-2012 and eGFRcombined-2021 showed the strongest associations with pre- and post-donation mGFR. Pre-donation eGFRcombined-2021 was most accurate for estimating both pre-donation (bias 0.01 ± 11.9 ml/min/1.73 m2) and post-donation mGFR (bias 1.3 ± 8.5 ml/min/1.73 m2). In donors with high/low muscle mass, cysC-based equations (with or without creatinine) performed better compared with equations based on only creatinine.

Conclusions: Combined eGFR equations yielded a better estimate of pre- and post-donation mGFR compared with estimates based on creatinine or cysC only. The added value of cysC seems particularly pronounced in donors with high or low muscle mass.