RESUMEN
PURPOSE: This study aimed to analyze the incidence of subclinical rejection (SCR) in kidney transplantation patients and risk factors associated with SCR. METHODS: We assessed 80 protocol biopsies taken within 2 years postoperatively in 41 adult patients who underwent living donor kidney transplantation between 2017 and 2020. All patients were on immunosuppressant therapy that included tacrolimus, mycophenolate mofetil, and steroids. RESULTS: The prevalence of Banff Borderline classification at 3, 6, and 12 months after transplantation was 4%, 5%, and 8 %, respectively, whereas none of the biopsies met the Banff criteria for acute T cell-mediated rejection throughout the study period. Active antibody-mediated rejection (ABMR) was only present in 8% of patients at 3 months after transplantation and chronic active ABMR at 6, 12, and 24 months after transplantation was detected in 10%, 13%, and 11% of the patients, respectively. Subgroup analysis revealed that 50% of the 6 patients with preformed anti-donor specific antibodies (DSAs) developed clinical or subclinical active ABMR within 3 months after transplantation, followed by chronic active ABMR according to serial histologic assessment. Conversely, only a small proportion of patients (3%) without preformed DSAs exhibited clinically active ABMR. CONCLUSIONS: SCR occurs too infrequently in patients with low immunologic risk and strong contemporary immunosuppression therapy to justify the diagnostic effort of serial protocol biopsies. However, protocol biopsies remain an indispensable tool in renal transplant monitoring and may be especially important in immunologically high-risk patients with pre-existing DSAs.