Associations between ABO incompatibility and the risk of cytomegalovirus, BK polyomavirus, and varicella-zoster virus infections after kidney transplantation: A systematic review and meta-analysis

Abstract

Viral infections, particularly cytomegalovirus (CMV), BK polyomavirus (BKV), and varicella-zoster virus (VZV) reactivation presenting as herpes zoster (HZ), represent major challenges following kidney transplantation. These infections pose considerable challenges for patients with ABO incompatibility, which may be associated with an increased risk of graft loss, increased morbidity, and possible mortality. The aim of this study was to determine whether ABO incompatibility increases the risk of CMV, BKV, and VZV infections among kidney transplant patients. A systematic review and meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Scopus, and Embase were searched for relevant studies published up to March 25, 2026. Study quality was assessed using the Newcastle–Ottawa Scale (NOS). Pooled odds ratios (ORs) and 95% confidence intervals (95%CI) were calculated using R software. The certainty of evidence for each outcome was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework, considering risk of bias, inconsistency, indirectness, imprecision, and publication bias. Of 7,433 articles identified, 26 studies involving 6,188 kidney transplant recipients were included in the final analysis. ABO incompatibility was associated with higher odds of CMV infection (OR: 1.34; 95%CI: 1.01–1.77; p=0.020) and BKV infection (OR: 1.84; 95%CI: 1.07–3.16; p=0.010). No statistically significant association was observed between ABO incompatibility and HZ (OR: 1.61; 95%CI: 0.95–2.72; p=0.070). No evidence of small-study effects was observed for BKV or VZV, whereas evidence of small-study effects was detected for CMV. The certainty of evidence was rated as very low for all outcomes according to GRADE. These findings suggest an association between ABO-incompatible kidney transplantation and increased odds of CMV and BKV infections. Given the observational design of the included studies and the use of unadjusted effect estimates, these findings should be interpreted as associations rather than evidence of a causal relationship.