Development of a novel South African rare donor red cell genotyping database

Abstract

More effective blood management can be implemented by issuing genotype-matched blood with a reduction in transfusion reactions and haemolytic disease of the newborn, since serological phenotyping methods for the detection of red cell antigens, while simple and easy to perform is limited by biological interference factors. Targeted rare donor screening using the frequency of rare types found amongst the ethnic groups as a guide will assist increase rare donor inventory. Currently, no such inventory exists in South Africa. The aim of this study was to develop a database to analyse and interpret red cell genotyping data using a novel molecular based red cell genotyping method at the South African National Blood Service (SANBS). AIMS AND OBJECTIVES The purpose of this study was to determine the prevalence of red cell genotypes and predicted phenotypes amongst the ethnic groups of blood donors at SANBS using the IDCOREXT red cell genotyping assay. This allowed for the identification of high and low prevalence antigens from commonly occurring red cell antigens, the probability of finding specific blood types depending on the prevalence in the population. The rare blood genotypes were identified and were used to establish a novel rare donor red cell genotyping database for SANBS and South Africa using a Business Intelligence (BI) IT program. METHODOLOGY Red cell genotyping data of 323 donors tested by means of the IDCOREXT assay from January 2015 to August 2016 was analysed using BIDSXT software. The ABO group, Rh types and ethnicity of 278 donors were imported to a Business Intelligence (BI) IT program after excluding seven invalid results and 38 confirmatory genotyping results and described. The Power BI programme was then used to exclude 44 serologically known rare donors prior to completing prevalence studies. High and low prevalence genotypes and predicted phenotypes for the remaining 234 donors were tabulated to ascertain the lowest percentage of positive or negative antigens in order to establish the rare blood types in each of the 10 blood groups per sample. Using Power BI, 161 rare blood types were identified from a total of 2340 genotyping results (234 samples, 10 blood groups) and was combined with the 44 serological known donors to develope the final rare donor red cell genotyping database comprised of 205 red cell genotyping results.. RESULTS The study population (n=278) included more males (61%) than females (39%) and the distribution of donors amongst the four major ethnic groups in South Africa was 48.9% White, 37.7% Black, 8.7% Indian and 4.7% Coloured similar to the current donor population in South Africa. Group O+ was the most prevalent blood group found in 76% of the study population. The most prevalent Rh phenotype was Ro (cDe/cDe) found in the majority of Black donors (60%, 50/84). The White donors showed the most Rh genetic variability with R1R2 found in White donors only (10%, 13/124) and R1R1 was most prevalent in Indians (57%, 12/21). The final rare donor red cell genotyping database comprised 205 donors and 13 high-frequency antigens were found: HrB-, HrS-, k-, Js(b-), Kp(b-), Jk(b-), Fy(b-), s-, S-s-U-, Joa-, Hy-, Yt(a-) and Lu(b-). Five positive lowfrequency antigens were identified: Cw+, Js(a+), Kp(a+), K+ and Uvariant. The rare Rh phenotype, RzR1 (CDE/CDe) was found in one Coloured donor. CONCLUSION This was the first study to determine the prevalence of red cell genotypes and predicted phenotypes amongst a subset of South African blood donors. In addition to new antigens identified and contributing to the international red cell genotyping database of rare donors, this study has now established a benchmark for similar studies to be completed on a larger scale.