Assessment of renal function in patients with renal transplantation by monitoring serum cystatin C

Objective To evaluate the value of monitoring serum cystatin C in assessment of renal function in patients with renal transplantation.Methods Serum cystatin C, creatinine (SCr), β2-microproglobin (β2-MG) and urea nitrogen (BUN) levels were determined at different time points (pre- or post-operation) in 58 renal transplant patients.Glomerular filtrated rate (GFR) was determined by using of 99mTc-DTPA at the seventh day after operation.The correlation between GFR and the four markers was analyzed.Diagnostic characteristics and ROC curve for the four markers were obtained using a GFR cut-off of 1.5 ml/s.Intra-individual coefficients of variation (CV) for cystatin C and SCr according to different time points during post-operation monitoring and the ratio (R) between CVSCr and CVcystatin C were calculated.Results Cystatin C was decreased by 48.1 % at the first day after operation, which was higher than others.The correlation coefficients between GFR and cystatin C, SCr, β2-MG, and BUN were 0.876, 0.691, 0.589, 0.516 respectively.Diagnostic characteristics for GFR and cystatin C, SCr, β2-MG, and BUN were as follows:sensitivity (91.3 %, 87.2 %, 82.6 %, 87.0 %); specificity (80.0 %, 69.2 %, 71.4 %, 42.9 %), positive predictive value (82.0 %, 73.7 %, 74.3 %, 60.4 %); positive likelihood rate (4.81, 2.83, 2.87, 1.53).The area under the curve (AUC) for GFR and cystatin C, SCr, β2-MG, and BUN was 0.914, 0.828, 0.803, and 0.765 respectively.The CVSCr was significantly lower than CVcystatin C (P＜ 0.01).R was less than 1 in most patients with cystatin C＜2 mg/L.In patients with cystatin C＞2 mg/L, R tended value 1 with increasing concentrations of cystatin C.Conclusion Cystatin C showes the best correlation to GFR, and is superior to the other markers in accurate in differentiate mild renal impairment from moderate and severe renal impairment.When renal function has minimal change, the cystatin C level has significant change.When the renal function has mild impairment, great changes in serum cystatin C indicate the unstable renal function. Key words: Kidney transplantation;  Serum cystatin C; Glomerular filtration rate