A Retrospective Study on Serologic Weak D Phenotype Among Rh-Negative Blood Donors Undergoing Indirect Antiglobulin Testing at a Tertiary Care Centre

Background: The Rh blood group system is highly significant in transfusion medicine, with the D antigen being the most immunogenic. Weak D, formerly termed Du, represents a quantitative reduction in D antigen expression and may lead to alloimmunization if not correctly identified. Determining the prevalence of serologic weak D among Rh negative donors is essential to enhance transfusion safety. The aim is to determine the prevalence of serologic weak D phenotype among Rh negative blood donors at a tertiary care centre. Material and Methods: This retrospective study was conducted over a three-year period from 2022 to 2024 at a tertiary care blood centre. A total of 10,653 blood donations were recorded. Of these, 609 donors were found to be Rh negative. Weak D testing was performed using the indirect antiglobulin test method with monoclonal Anti D reagents. Agglutination after the addition of anti-human globulin was considered confirmatory for weak D positivity. Prevalence was calculated as a percentage of Rh negative donors. Results: Among the 10,653 donors, 609 (5.72 %) were Rh negative and 10,043 (94.28 %) were Rh positive. Of the 609 Rh negative donors, 18 were confirmed as weak D positive, yielding a prevalence of 2.96 %. Weak D positivity was found in all ABO blood groups and highest proportion was observed in A negative donor (5.52 %). Conclusion: The prevalence of serologic weak D among Rh negative donors in our centre was 2.96 %. Routine weak D testing in Rh negative donors is essential to prevent misclassification and reduce the risk of alloimmunization, thereby ensuring safer transfusion practices.

Keywords: Weak D; Rh-negative donors; Indirect antiglobulin test; Blood transfusion; Alloimmunization.