Serum cystatin C in renal transplant patients

Assessment of renal function in clinical medicine is of great importance especially in patients with renal transplants. Cystatin C has the characteristics of an ideal marker to assess renal glomerular filtration rate. Forty patients with renal transplants under steady-state post-transplant conditions were included in the study. Steady-state was defined as lack of acute rejection periods during the last 6 months and stable cyclosporin A medication during the past 4 weeks. Gender was balanced with 20 male and 20 female patients, the mean age was 51 +/- 14 years, time since transplantation was 5 +/-3.5 years. Fifteen percent of the patients suffered from diabetes mellitus. Immunosuppression consisted of cyclosporin A, imuran, and prednisolon. To assess renal function cystatin C, creatinine clearance, serum creatinine, and serum beta (2)-microglobulin were tested. Creatinine was analysed in serum and urine to calculate the creatinine clearance related to 1.73 m(2) body surface. Cystatin C and beta (2)-microglobulin were determined by using a particle-enhanced turbidimetric assay. Cystatin C correlated best with creatinine clearance (r = 0.66), beta (2)-microglobulin (0.57), and serum creatinine (0.56). The diagnostic accuracy of cystatin C was significantly better than serum creatinine (p<0.05), but did not differ significantly from creatinine clearance (p=0.73), and <beta>(2)-microglobulin (p=0.46). Our data show that patients with renal transplants, cystatin C has a similar diagnostic value as creatinine clearance. However, it is superior to serum determination of creatinine and beta (2)-microglobulin. Cystatin C allows for rapid and accurate assessment of renal function in patients with renal transplants and is clearly superior to the commonly used serum creatinine. (C) 2001 Elsevier Science B.V. All rights reserved.