The Prevalence of Syphilis, HTLV I/II, and Malaria Among Blood Donors at the Riyadh Regional Laboratory: A Retrospective Study from Saudi Arabia

Background: Transfusion-transmitted infections (TTIs) continue to threaten the safety of blood supply systems worldwide. This study aimed to estimate the prevalence of malaria, HTLV I/II, and syphilis among blood donors at the Riyadh Regional Laboratory and Blood Bank from 2018 to 2022, and to assess associations with gender, age, nationality, and the ABO/RhD blood group. Methods: We conducted a retrospective analysis of 217,543 blood donations. Demographic and serological records were extracted from the blood bank’s electronic database and analyzed in SPSS v28. Chi-square, Fisher’s exact tests and multivariate logistic regression were used as appropriate, with significance set at p < 0.05. Results: Male donors accounted for 97% of the cohort, and 52% were non-Saudi nationals. Malaria was rare (0.03%; n = 58); all 58 cases were detected in 2018, and none were recorded in subsequent years. HTLV I/II antibodies were observed in 464 donors (0.21%), with the highest annual share in 2019 (39.7%). Syphilis was the most common TTI, identified in 1143 donors (0.52%), and showed a significant increasing trend over the study period (Cochran–Armitage test p < 0.001; Poisson regression IRR 1.21, 95% CI 1.15–1.28, p < 0.001). In multivariable logistic regression, non-Saudi nationality was independently associated with syphilis positivity (aOR 1.48, 95% CI 1.31–1.67), and ages 46–65 was associated with higher odds of all three TTIs. ABO and RhD blood groups were not significantly associated with TTI positivity in univariate or multivariable analyses. Conclusions: Current screening practices appear to maintain low TTI prevalence in the central region, but the rising syphilis trend and the clustering of malaria positivity among non-Saudi donors point to the need for closer surveillance and targeted donor counseling. The study also highlights the need for more granular demographic data collection, including specific country of origin and duration of residence, to enable more effective risk stratification and intervention targeting.