Can cystatin C become an easy and reliable tool for anesthesiologists to calculate glomerular filtration rate?

Background And Aims: The aim was to evaluate the role of cystatin C as a noninvasive and easy marker of glomerular filtration rate (GFR) estimation in voluntary kidney donors.

Materials And Methods: We retrospectively evaluated 40 voluntary kidney donors. They underwent complete biochemical and nuclear tests as a part of transplant workup. Serum cystatin C, serum creatinine, and Tc-99m diethylene-triamine-penta-acetic acid (DTPA) were used in our study. We calculated GFR using the chronic kidney disease epidemiology collaboration (CKD-EPI) formula based on creatinine only (GFR-CKD-EPI-creat), CKD-EPI formula using creatinine and cystatin C (GFR-CKD-EPI-cyst-creat), and modification of diet in renal disease (MDRD) and CKD-EPI cystatin C equation (2012) (GFR-cyst). Data was evaluated using the SPSS software (version 11.5). The correlation analysis and analysis of variance was used for statistical computation. Agreement was determined using analyze-it version 2.30 for MS-Excel 12+.

Results: The mean age of the donors in our study was 49.83 ± 13.06. The mean cystatin C in females was 0.72 ± 0.12, the mean cystain C in males was 0.87 ± 0.23. On correlating GFR-cyst with GFR-DTPA the Pearson correlation coefficient (ρ) was found to be 0.388 this correlation was significant with P < 0.05. While comparing with DTPA the correlation coefficient of GFR-CKD-EPI-creat group was 0.587 which was significant with P < 0.01. The correlation coefficient of GFR-CKD-EPI-cyst-creat group compared with GFR-DTPA group was 0.543 which was also significant at P < 0.001. GFR-CKD-EPI-creat gave the highest correlation with DTPA in our study. The correlation coefficient of GFR-MDRD group with DTPA group was 0.576 this correlation was also significant with P < 0.01. The results obtained were further statistically analyzed by Bland-Altman analysis the percentage error for GFR-DTPA versus GFR-cyst-creat is 29.72%; for GFR-DTPA versus GFR-EPI-creat is 30.73%; or GFR-DTPA versus MDRD is 31.63% and for GFR-DTPA versus GFR-cyst is 34.37%.

Conclusion: Cystatin C is a good endogenous marker for calculating GFR as it correlates very well with DTPA and CKD-EPI equation based GFR.