Abstract
Unexpected red blood cell (RBC) alloantibodies can lead to hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN). Screening for these antibodies is essential to ensure transfusion safety and improve patient care. Prevalence and frequency of unexpected antibodies vary among populations, influenced by genetic and demographic factors. This study addresses the gap in data specific to University Hospital, General Sir John Kotelawala Defence University. A retrospective analysis was performed on 20,212 patients (40.74% pregnant women and 59.25% transfusion recipients) from November 2019 to August 2024, assessing the prevalence, distribution, and clinical relevance of RBC alloantibodies. The study found that 0.80 percent of patients were alloimmunized and 28.87 percent of the antibodies were clinically significant. Common antibodies included anti-Leb (27.27%) and anti-Lea (19.25%); anti-D was the most frequent among Rh antibodies. A significantly higher proportion of pregnant women were alloimmunized compared with transfusion recipients (p < 0.000). Among D– pregnant women, 5.45 percent were alloimmunized, mainly with anti-D. HDFN was identified with either maternal anti-D or anti-E. These findings emphasize the need for early antibody detection and monitoring to enhance transfusion safety, suggesting policy improvements for antibody screening in transfusion and antenatal care in Sri Lanka.