Prevalence of Weak D Antigen in Rh Negative Blood Group: An Experience at a Tertiary Blood Centre in Bengaluru, Southern India

Abstract

Introduction: The Rh blood group system, consisting of more than 50 different antigens, is the most polymorphic among human blood types. Among them, D is the most important antigen. The incidence of weak (Du) antigens ranges from 0.2 to 1%. Routine screening for RhD does not cause agglutination with anti-RhD serum; therefore, it must be detected using anti-human globulin serum. Due to the potential immunological reaction of Du-positive cells in RhD-negative individuals, it is crucial to emphasise the therapeutic implications of this finding and its relation to the risk of alloimmunisation. Aim: To determine the frequency of the Du antigen among RhD-negative individuals. Materials and Methods: This five-year hospital-based cross-sectional study was conducted from January 2017 to January 2022 in the Department of Transfusion Medicine at ESIC MC and PGIMSR, Bengaluru, Karnataka, India. ABO and Rh blood group samples were collected in EDTA vacutainers from the blood collection centre and sent to the Department of Transfusion Medicine. Data analysis was performed using Microsoft Excel. Results were presented as numbers and percentages. ABO and Rh blood group typing were carried out using the tube method (immediate spin tube technique), and negative samples were further tested for weak D (Du) using the Gel card system. The Rh-negative cases with Du testing were recorded, and the frequency of the Du antigen in Rh-negative blood group types was determined. Results: A total of 69,282 blood samples were analysed, of which 66,442 (95.90%) were Rh positive, and 2,840 (4.10%) were Rh negative. The male-to-female ratio was 1:1.79. Out of the total 2,840 Rh-D negative samples, 31 samples were weak D positive. Among them, 06 (0.85%) belonged to the A blood group, 12 (1.63%) to the B blood group, 12 (1.01%) to the O blood group, and 1 (0.47%) to the AB blood group. The Du positivity noted among the Rh-negative cases was 1.09%. The overall Du positivity noted among all the samples was 0.045%. Conclusion: To prevent RhD mismatches, which can lead to life-threatening complications, it is advised to retype all Rh-negative blood samples using a Du test during routine grouping. This is because weak D antigen is immunogenic and capable of producing alloimmunisation if transfused to RhD-negative individuals.

Keywords

• alloimmunisation
• agglutination
• du antigen
• gel card system