ERYTHROCYTE ALLOIMMUNISATION AND THE PHENOTYPIC DIVERSITIES OF CLINICALLY SIGNIFICANT BLOOD GROUP ANTIGENS IN SICKLE CELL ANAEMIA PATIENTS IN KILIFI, KENYA

Abstract

Sickle cell anaemia (SCA) is a severe monogenic disorder that results in abnormal hemoglobin with sub-Saharan Africa bearing 75% of the global burden. Blood transfusion is an integral part of patient management and the lack of alloantibody screening or extended matching beyond ABO and RhD prior to transfusion in Kenya is likely to increase the risk of developing erythrocyte alloantibodies. The burden of alloimmunisation and the phenotypic diversity of clinically significant blood group antigens among individuals with sickle cell anaemia seeking care at the Kilifi County Referral Hospital (KCRH) is unknown. This study aimed to determine the prevalence of alloimmunisation and the diversity of clinically significant blood group antigens in SCA patients in Kilifi. The study included a retrospective cohort of 98 children with SCA aged 0-13 years who were admitted to KCRH between 2003 and 2023, and a cross-sectional survey of 226 regular attendees of the sickle cell clinic between 2023 and 2024. Plasma samples obtained were screened for alloantibodies using standard 3-ID-Diacell, and identification was done using ID-diapanel cells. Participant erythrocytesfor the cross-sectional survey were phenotyped for 22 erythrocyte antigens using commercial reagents, using standard serologic techniques from DiaMed GmbH, Switzerland, Bio-Rad. Alloantibodies were detected in 14/98 (14.3%) participants included in the retrospective study period, while for the cross-sectional survey, alloantibodies were detected in 13/226 (5.8%) participants. Fourteen alloantibodies were identified in both study designs: three anti-E, three anti D, two anti-M, whereas anti-S, anti-s, anti-Lua, anti-Lea, and anti-Leb were found in one individual each. Older age was significantly associated with the development of antibodies (P = 0.02 in the retrospective analysis and P = 0.04 in the cross-sectional analysis). The Rhesus and MNS blood groups exhibited diverse phenotypes, with R0r (ccD.ee) having the highest frequency of 56.4%, with R1R1 (CCD.ee), R1R2 (CcD.Ee), and R2Rz (CCD.EE) as the rarely expressed Rh phenotypes. M+N+S-s+ was expressed (36.7%), and M+N+S+s-, M-N-S-s+ were rarely expressed MNS phenotypes. Other rare phenotypes in Kell, Lewis and Duffy were K+k+, Le(a+b+) and Fy(a+b+), respectively. xv These study results underscore the importance of routine alloantibody screening and the need for extended antigen matching in SCA patients to enhance transfusion safety, particularly those expressing rare phenotypes or are frequently transfused.