Extended red cell antigen frequencies in a Southwestern Colombian donor population: Implications for phenotype-matched transfusion strategies

BACKGROUND AND AIMS: The complex history of genetic admixture in Latin American populations creates unique erythrocyte antigen profiles. This study aimed to determine the extended red blood cell (RBC) antigen frequencies in a blood donor population from Southwestern Colombia, a region with significant African ancestral heritage, to support phenotype-matched transfusion strategies and optimize donor selection. MATERIALS AND METHODS: A cross-sectional study was conducted on 501 voluntary blood donors at a highly complex hospital blood bank in Cali, Colombia. Extended serological phenotyping for the Rh, Kell, Kidd, Duffy, MNS, Lutheran, Lewis, and P blood group systems was performed using automated gel card assays. Antigen and phenotype frequencies were determined, and low-frequency profiles relevant to transfusion compatibility were identified. RESULTS: The donor cohort (60.3% female, median age 24 years) exhibited substantial antigenic diversity. Key antigen frequencies included D (92.0%), e (95.2%), c (77.8%), C (67.3%), E (62.9%), and a remarkably low prevalence of the K antigen (4.2%). Within the Duffy system, 5.4% of the population expressed the Fy(a-b-) phenotype, confirming the strong demographic influence of African heritage in the region. Operationally important rare phenotypes were successfully identified, including Fy(a-b-) (n = 27), Lu(a+b-) (n = 2), k- (n = 1), and M-N + S-s- (n = 1). CONCLUSION: The distinct antigenic variability observed in Southwestern Colombia underscores the limitations of relying on foreign reference frequencies for local transfusion practices. Developing regional immunohematologic databases and coordinated rare donor registries is essential to optimize extended serologic matching, ensure the timely provision of compatible units, and mitigate alloimmunization risks for chronically transfused patients.