The findings of this study show that the blood group O occurs most frequently among the donors and blood group AB is the least common in southwestern Uganda. Knowledge of the distribution of ABO and Rhesus blood groups is an important element in determining the direction of recruitment of voluntary blood donors as required in each region and for effective management of blood banks inventory, be it at a facility of a small local transfusion service or regional or national transfusion services. It is therefore imperative to determine and have information on the distribution of ABO and Rhesus blood group systems of different ethnic groups in any population where blood transfusion services are being offered.
These findings are consistent with studies done elsewhere in Africa [15, 16]. A similar distribution of ABO blood groups have been seen in studies conducted among the Bangladesh population, Western Europeans, the African-American and Caucasian population of America [11, 17, 18] although the proportion of blood group O was slightly below 50%, ranging from 40 to 47%. Other studies in Australia by red cross society , and in USA by Mollison PL et al. [5, 28] have shown the commonest blood group was O, followed by A, B and AB, also consistent with our study findings. Unlike a study conducted elsewhere in Africa, this study did not determine the distribution of ABO and Rhesus group by ethnic group .
However, in contrast to our study, studies conducted in India  and Pakistan  showed blood group B was the most predominant, followed by blood group O, A and AB. While another study done in Nepal by Pramanik et al.  found the commonest blood group as group A, followed by blood group O, B and AB. In all the studies cited and including our study, blood group AB is the least distributed among the population of the world.
This study reveals that Rhesus (D) negativity has the lowest distribution among the donors which is similar to other studies conducted on other African continent. The identification of Rhesus blood system is important to prevent erythroblastosis fetalis, which commonly arises when a Rhesus negative mother carries Rhesus positive fetus. With the low incidence of Rhesus negativity in our setting the number of cases of haemolytic disease of the newborn (HDN) are expected to be much lower. Worlledge et al.  also found a low incidence of Rhesus negativity among the Nigerians, between 1.69 and 5.5%. Collectively these findings confirm low incidence of Rhesus (D) negative among the African population.
The frequency of Rh negativity, is less in Africans, Asians (mainly Chinese) and American blacks compared to Caucasians . In most parts of India, the incidence of Rhesus (D) negative blood group varies from 2 to 6%. About 5–11% of donors all over the world are detected as Rhesus (D) negative except in Britain and USA, where the distribution of Rhesus (D) negative is 15 and 17% respectively [5, 28].
In this study there was no difference distribution of donors among the ABO blood groups by gender. However a higher proportion of Rhesus (D) negative was found among the male donors. It was also observed that males in southwestern Uganda constitute the majority group of blood donors. A similar trend has been observed elsewhere in Africa  and many parts of India [25, 26]. The dominance of male over female in blood donation exercise can be attributed to the fact that in an African context there is a general belief that men are healthier than women  and thus are more suitable for blood donation. Women in menstruating age group lose blood every month and are anemic, so unfit for blood donation and are eliminated by the pre-donation screening exercise. Other obstetrical factors including pregnancy and breastfeeding render them further from donating blood. In India social taboo, cultural habits, lack of motivation and fear of blood donation have been cited as some of the reasons why female donors are very few . However for southwestern Uganda, these findings suggest that emphasis should now be placed on recruitment of female donors to improve supplies of Rhesus (D) positive blood.
In contrast to findings of studies elsewhere that demonstrate males as the most prevalent donors, our study results show that non-adult females in Uganda constitute the majority of donors. About 85% of Uganda’s voluntary non-remunerated blood donors are of school going age, to which the non-adult females belong because of the government’s policy on affirmative action and women emancipation. Further the pre-donation education given to potential donors in Uganda targets women encouraging them to donate willingly.
The sequence of ABO distribution among the rural population in southwestern Uganda is; O > A > B > AB. While the frequency of Rhesus (D) negative is very low in rural southwestern Ugandan and is mainly among males. Further, males are the predominant blood donors in the region. The blood bank services in southwestern Uganda need to develop innovative strategies targeting female donors. This is likely to boost stocks for the blood bank in the region and also minimize the collection of Rhesus (D) negative supplies. Similar studies should be undertaken for the other regions of the country to establish the blood group distribution. Collectively these studies would provide the national blood bank services with information critical for supply forecasting and blood inventory management.