Clinical value of cystatin c and beta trace protein in glomerular filtration rate in renal transplant cases with stable renal graft functions; comparison by TC 99M dtpa plasma sample method

Glomerular filtration rate (GFR) is the best indicator of the renal function. Therefore, measurement of the graft?s GFR is of paramount importance in renal transplantations. Gold standard for GFR measurement is inulin clearance. However, its measurement is inconvenient, time-consuming, and non-economic. Thus, in both scientific studies and routine clinical practice Nuclear medicine methods (Tc-99m DTPA, Cr-51 EDTA) are preferred, which are highly correlated with inulin clearance. In addition, recently cystatin C (cys C) and beta trace protein (BTP) are also used for this purpose. In literature, however, data are limited about the clinical value of cys C and BTP in GFR measurement in renal transplant cases and the results have been inconclusive. In this study, we aimed to determine the efficiency of cys C and BTP in determination of GFR in transplant patients with stable renal graft functions.A total of 89 (60 males, 29 females) renal transplant patients aged 19 to 67 years (mean 38.15 years) were included, who had undergone renal transplantation at least 6 months before study enrollment and had stable graft functions according to clinical and laboratory criteria. GFR was calculated with three different methods: 1) Using the gold standard Tc-99m DTPA two plasma sample method; 2) Using 8 different formula containing cys C (mg/l) to calculate GFR; 3) Using 3 different formula containing BTP (mg/l).Correlation of GFR values calculated with cys C and BTP with that obtained with Tc-99m DTPA two plasma sample method was assessed. GFRs calculated with both methods were significantly correlated with that calculated with gold standard method. However, GFR values obtained with cys C had a better correlation compared to those of BTP. Also using regression analysis, performances of cys C and BTP in predicting GFR calculated with Tc-99m DTPA two plasma sample method were compared and a p value < 0,01 was obtained for cys C and 0,706 for BTP. Using Bland Altman analysis, scatter graphics of the differences between GFR values calculated using Tc-99m DTPA two plasma sample method and those calculated with cys C, BTP at a confidence interval of 95% (mean±1.96SD). The GFR value obtained with cys C had the most reliable consistency.As a conclusion, we showed that cys C may be a good marker for GFR of transplanted kidney. We also found that GFR value calculated with BTP failed to show GFR of the transplanted kidney. Based on these results, our study demonstrated that cys C is superior to BTP in reflecting GFR