*Purpose: The purpose of this study is to explore the risk factors associated with the development of chronic active antibody mediated rejection (CAAMR) after the kidney transplantation.

*Methods: The study cohort included 171 recipients who had been followed up over 1 year after the kidney transplantation among 269 recipients who underwent allograft biopsies between January 2016 and December 2017. The pathological diagnosis was performed according to the Banff 2013 criteria. The cohort included 21 patients who were diagnosed with pathological CAAMR, irrespective of the DSA presence, and 150 patients without any evidence of allograft rejection. We determined high- or low-dose of mycophenolate mofetil (MMF) by using the median dose as the cutoff (17.5 mg/kg/day).

*Results: The cohort was divided into two groups with or without diagnosis with CAAMR and evaluated the potential risk factors, including MMF dose (high vs low), duration after the transplantation, cyclosporine vs tacrolimus, past history of acute rejection, ABO incompatibility, the presence of preformed DSA (pDSA) (Table 1). The univariate analyses revealed that the low-dose of MMF and the presence of pDSA were significant risk factors (Chi square, p= 0.037 and p= 0.001, respectively). The duration after transplantation was significantly different between the groups. The multivariable logistic regression analysis revealed that low-dose MMF, pDSA, and duration after the kidney transplantation were independent risk factors for the development of pathological CAAMR (Odds ratio, 4.97 [95% CI: 1.09-22.68], 29.12 [95% CI: 4.62-183.5], 1.000696 [95% CI: 1.000378-1.001014], respectively) (Table 2).

*Conclusions: Low-dose MMF (< 17.5 mg/kg/day) as well as the presence of pDSA are significant risk factors for the development of CAAMR. Thus, caution is warranted against reducing the dose of MMF, especially in recipients with preformed DSA and longer follow-up period.

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