Background: Cytomegalovirus (CMV) is a risk factor for acute renal allograft rejection. The aim of this study was to determine the impact of CMV viremia on subclinical rejection (SCR) and interstitial fibrosis and tubular atrophy (IF/TA) in protocol biopsy at 3 months after transplantation.

Methods: A total of 118 consecutive renal transplant recipients at risk for CMV (donor and recipient CMV seropositive) were included and followed up prospectively. Protocol biopsies with sufficient tissue were obtained in 102 patients. CMV activity was monitored using real-time polymerase chain reaction in whole blood. Three-month prophylaxis with valacyclovir or ganciclovir was given in 60 patients, whereas the remaining 42 patients were managed by preemptive therapy. Multivariate logistic stepwise regression analysis was used to estimate the effect of CMV viremia and other covariates on SCR and IF/TA.

Results: CMV viremia occurred in 41% of the patients with a median peak viral load of 1300 copies/mL. The incidence of SCR and IF/TA was 29% and 28%, respectively. CMV viremia was not a risk factor for SCR (OR=0.77, P=0.551); however, viremia of more than or equal to 2000 copies/mL increased the risk of IF/TA (OR=3.83, P=0.023). Biopsy-proven acute rejection (OR=3.34, P=0.009) and sirolimus-based immunosuppression (OR=6.13, P=0.008) were independent predictors of SCR. Delayed-graft function (OR=6.02, P=0.001) and donor age (OR=1.53 per 10-year increase, P=0.009) were associated with IF/TA.

Conclusions: CMV viremia is not an independent risk factor for SCR. CMV viremia with viral load of more than or equal to 2000 copies/mL is associated with increased risk of IF/TA in protocol biopsy at 3 months after transplantation.