Frequency and distribution of ABO and Rh blood group systems among blood donors at the Northern Zone Blood Transfusion Center in Kilimanjaro, Tanzania: a retrospective cross-sectional study

OBJECTIVES: ABO and Rh blood group systems are the major factors affecting the blood transfusion safety. The frequency and distribution of these blood group systems vary worldwide. We aimed to determine the frequency and distribution of ABO and Rh blood group systems among first-time blood donors at the Northern Zone Blood Transfusion Center in Kilimanjaro, Tanzania. DESIGN: Cross-sectional descriptive population-based study. SETTING: Data on ABO and Rh blood group systems were obtained and analysed from the Northern Zone Blood Transfusion Center among first-time blood donors. PARTICIPANTS: There were 65 535 first-time blood donors aged 15–55 years who donated at the Northern Zone Blood Transfusion Center from January 2017 to December 2019. OUTCOME MEASURES: The percentage of ABO and Rh blood group systems among different categories of blood donors was calculated. RESULTS: Retrospective data from Blood Establishment Computer System of 65 535 first-time blood donors were analysed in the present study. The mean age of the blood donors was 30.6±11.2 years (range: 15–55 years). The vast majority of the blood donors 84.2% (n=55 210) were men. Also, the majority 69.6% (n=45 595) were aged ≥35 years. Blood group O was the most common blood group which was found in over half 52.4% (n=34 333) of the blood donors and majority 95.3% (n=62 461) of the donors were Rh positive. Moreover, the majority 78.3% (n=51 336) were voluntary donors and the remaining 21.7% (n=14 199) were replacement donors. CONCLUSION: Majority of the donors had blood group O and also the vast majority of the donors were Rh positive. Considering the large size of our study population, this has provided a more comprehensive information regarding the frequency and patterns of ABO and Rh blood group systems in Tanzania. The observed association of blood group A with one of the regions from which donors were coming from, is intriguing and further studies may confirm possible related genetic evolution.