Analysis of the dynamic changes in serum cystatin C(Cys-C) and β2-microglobulin(β2-MG) levels in the early period after renal transplantation, and evaluation of their diagnostic value for the recovery of graft renal function.

A total of 70 patients who underwent allogeneic kidney transplantation in the Second People′s Hospital of Shanxi Province from June 2018 to December 2020 were retrospectively collected as the transplant group. 30 healthy physical examination subjects in the same period were randomly selected as the control group. Blood samples were collected from the transplantation group before operation, and at 1, 7, 14 and 30 days after operation, while fasting blood samples were collected from the control group on the day of physical examination. The levels of serum creatinine (SCr), blood urea nitrogen (BUN), Cys-C, β2-MG, and estimated glomerular filtration rate (eGFR) were measured, respectively. Differences in quantitative variables within groups were analyzed using repeated-measures ANOVA, and intergroup comparisons were conducted with the independent samples t-test. Pearson correlation analysis was used to examine the linear association. A combination of logistic regression and receiver operating characteristic (ROC) curve analysis was performed to assess the integrated diagnostic value of Cys-C and β2-MG for renal allograft function.

All parameters (SCr, BUN, Cys-C, β2-MG, eGFR) in the transplant group at pre- and post-transplant stages differed significantly from controls (all P< 0.01). Within 30 days post-transplant, SCr, BUN, Cys-C and β2-MG in recipients continuously decreased while eGFR steadily increased, with all changes statistically significant vs. baseline (all P< 0.01). Pearson correlation analysis showed that BUN, Cys-C, and β2-MG were significantly negatively correlated with eGFR (r=-0.719, -0.780, and -0.711). ROC curve analysis demonstrated that the areas under the curve (AUC) of Cr, BUN, Cys-C, and β2-MG for evaluating renal allograft function were 0.955 (95%CI: 0.936-0.975), 0.940 (95%CI: 0.917-0.963), 0.992 (95%CI: 0.984-0.999), and 0.918 (95%CI: 0.891-0.945), respectively (all P<0.01). The optimal cutoff value of Cys-C was 1.305 mg/L, with a sensitivity of 0.996 and specificity of 0.966. For β2-MG, the sensitivity and specificity at the cutoff value were 0.826 and 0.922, respectively. The AUC of combined detection of Cys-C and β2-MG for diagnosing renal allograft function was 0.991 (95%CI: 0.983-0.999, P<0.01).

Cys-C is a superior indicator for evaluating the early recovery of renal allograft function. Compared with Cys-C alone, the combined detection of Cys-C and β2-MG shows no significant advantage in evaluating the early recovery of renal allograft function after renal transplantation.