BACKGROUND: Creatinine is a standard marker for estimation of the transplanted kidney function. Concentration values are used in mathematical equations for GFR (glomerular filtration rate) calculation, with MDRD (modification diet in renal disease) being most commonly used. Cystatin C is an alternative marker for changes in glomerular filtration, which is also used in eGFR (estimated GFR) formulas. The aim of this study was to reveal eGFR <60 ml/min/1.72 m^2 in a population of patients after renal transplant, with stable graft function, using different formulas.

MATERIAL AND METHODS: A group of 100 patients (56 females and 44 males) aged 20–78 years, took part in this study. Renal transplantation was conducted from 10 years to 10 months prior to the study. Estimated GFR was calculated with 4 formulas: MDRD, CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration), CKD-EPI cys (using cystatin C), and CKD-EPI mix (using creatinine and cystatin C). We used electronic calculators available on the National Kidney Foundation and the Nephron Information Center websites.

RESULTS: The occurrence of eGFR values <60 ml/min/1.73 m^2 was 28% according to MDRD formula, 23% according to CKD-EPI, 25% according to CDK-EPI cys, and 26%according to CDK-EPI mix.

CONCLUSIONS: Occurrence of GFR <60 ml/min/0.73 m^2 was the highest when calculated by MDRD formula, and the lowest when calculation was done with CDK-EPI. The significant discrepancy with different eGFR formula testing suggests the need for further research to find the best marker and/or formula for graft function estimation.

Keywords: cystatin C, Glomerular Filtration Rate, Kidney Transplantation