ABO blood group associations with corneal and organ failure diagnoses on the Ecuadorian transplant waiting list: A 2017-2022 observational cohort study.

BACKGROUND: ABO antigens are broadly expressed on endothelial and epithelial glycoproteins and modulate innate immune responses, complement activation, tissue immunogenicity, and endothelial-derived haemostatic factors. Their differential distribution across the specific diagnoses that lead to end-stage organ failure has been little explored in Latin American populations, where a high prevalence of group O provides a distinct genetic background to examine these associations. We report an exploratory analysis in national transplant waiting list of Ecuador. METHODS: We conducted a retrospective study of 4408 patients on Ecuador's national transplant waiting list (2017-2022) who had a known ABO group. The sample included kidney (n = 2326), cornea (n = 1733), liver (n = 323), heart (n = 22), and lung (n = 4) transplant candidates. We tested associations using Fisher's exact test (simulated p-values with 5000 replicates), Cramér's V with bootstrap 95% CI, binary logistic regression (O vs. nonO), and a goodness-of-fit test against Ecuadorian population frequencies. We corrected for multiple testing with the Benjamini-Hochberg method. RESULTS: Three ABO associations remained significant after correction: ABO with corneal diagnosis (p_BH = 0.007; V = 0.110), ABO with organ type (p_BH = 0.004; V = 0.059), and ABO with age at waitlist entry (p_BH = 0.014; V = 0.061). Residual analysis showed that groups A and AB were more frequent than expected among patients with type 2 diabetes as the cause of end-stage renal disease (r = +2.80 and +3.18), while group O was less common (r = -2.66). In corneal patients, group A was underrepresented in adherent leukoma (r = -2.26) and vesicular keratopathy (r = -2.04). Liver disease showed no ABO signal (p = 0.996). No Rh-related association survived multiple-testing correction, supporting the specificity of the ABO signal. CONCLUSIONS: The ABO blood group appears to have an uncharacterized, organ-specific effect on end-stage organ and corneal failure. In our analysis of transplant candidates, the corneal association survived multiple-testing correction and remained robust in the sensitivity analysis for missing ABO data. Groups A and AB were enriched among patients with type 2 diabetes as a cause of end-stage renal disease, and group A was underrepresented in adherent leukoma and vesicular keratopathy. No association was detected in hepatic disease, and no Rh-related association was significant after correction.