Introduction: Estimation of kidney function is crucial in appropriate and safe qualification living kidney donors. Glomerular filtration rate (GFR) measurement with exogenous substances is an invasive and expensive procedure. Alternatively, kidney function can also be assessed by GFR estimation formulas, which base on serum creatinine and other novel markers such as cystatin C and beta trace protein (BTP).
Aim: The aim of the study was to compare accuracy of different formulas estimating GFR with reference scintigraphy-measured GFR in population of living kidney donor candidates. Material and Methods There were 30 living kidney donor candidates (aged 26-68, median 47) enrolled into the study. GFR was measured using following formulas: Cockroft-Gault, MDRD, CKD-EPI creatinine, CKD-EPI cystatin C, CKD-EPI creatinine-cystatin, Poge, Mayo QF, Nankivell, Larson, Taan, BTP-White. For reference GFR was assessed using 99mTc-DTPA. Statistical analysis was performed using STATISITICA 12 software.
Results: 20% margin of reference was held in about 50% of cases in most formulas. Almost all formulas (besides Cockroft-Gault, Mayo QF and BTP-White) had a statistically significant positive correlation with reference. However, among patients with BMI>25 kg/m2 BTP-White formula had the strongest correlation with reference (r=0.59; p=0.016). Among older patients formulas based on cystatin C, such as Larson and Taan had the strongest correlations (r=0,59; p=0,02 for both formulas). Conclusion In living kidney donor candidates GFR estimation formulas should be chosen individually. The strongest correlation with scintigraphy-measured GFR among overweight patients has BTP- White formula and among older patients formulas based on cystatin C.