The Trend of Serum Creatinine Does Not Predict Follow-Up Biopsy Findings Among Kidney Transplant Recipients With Antibody-Mediated Rejection

Traditionally, antibody-mediated rejection (AMR) has been suspected mainly by a rise in serum creatinine (Scr) and confirmed by allograft biopsy. There is limited literature describing the trend of Scr after treatment, and how that trend might differ between patients with histological response and with no response to treatment. METHODS. We included all cases of AMR at our program between March 2016 and July 2020 who had a follow-up biopsy after the index biopsy, with initial diagnosis of AMR. We trended the Scr and change in Scr (delta Scr) and its association with being a responder (microvascular inflammation, MVI ≤1) or nonresponder (MVI >1), as well as graft failure. RESULTS. A total of 183 kidney transplant recipients were included, 66 in the responder group and 177 in the nonresponder group. The MVI scores and sum chronicity scores, along with transplant glomerulopathy scores, were higher in the nonresponder group. However, Scr at index biopsy was similar in responders (1.74 ± 0.70) versus nonresponders (1.83 ± 0.65; P = 0.39), as were the delta Scr at various time points. After adjustment for multiple variables, delta Scr was not associated with being a nonresponder. Also, delta Scr value at follow-up biopsy compared with index biopsy among responders was 0 ± 0.67 (P = 0.99) and among nonresponders was –0.01 ± 0.61 (P = 0.89). Being a nonresponder was significantly associated with an increased risk of graft failure at the last follow-up in univariate analysis but was not in multivariate analysis (hazard ratio 1.35; 95% confidence interval, 0.58-3.17; P = 0.49). CONCLUSIONS. We found that Scr is not a good predictor of the resolution of MVI, supporting the utility of follow-up biopsies after treatment of AMR.