Frequency of DEL phenotype in RhD negative donor population of north India

Background: There is a paucity of data for DEL phenotype in the Indian population. Ours is a tertiary care Regional Blood Transfusion Centre in north India collecting more than 50,000 blood units out of which 8-9% are RhD negative donors.

Aim: To determine the frequency of DEL phenotype in RhD negative blood donor population at our centre.

Material and methods: A total of 200 RhD-negative blood donor samples were included in this study which was conducted over a period of 4 months (October 2013 to January 2014). All these blood samples were tested for extended Rh typing including C, E, c and e antigens and also for adsorption elution testing. The heat elution method at 56 °C in water bath for 10 minutes was utilized. The eluate and the last wash supernatant were used for indirect antiglobulin test against O RhD positive and O RhD negative cells by gel technique using the LISS Coombs' AHG gel cards (Biorad, Morat, Switzerland). Those donor samples which were found positive on adsorption elution testing were also further investigated by gel technique for Direct Antiglobulin test (DAT), Weak D testing and Auto Control test.

Results: Out of the total 200 Rh D negative donor samples tested, 3 (1.5%) samples were found to give positive result and, thus, were the DEL phenotypes. It was found that 20 (10%) donor samples were positive for C antigen, 5 (2.5%) for E antigen, 200 (100%) for c antigen and 200 (100%) for e antigen. Among the DEL negative (= 197), 193 (98%) were E antigen negative and only 4 (2%) were E antigen positive, whereas among the DEL positive samples (= 3), 2 (66.6%) were E antigen negative and 1 (33.3%) was E antigen positive. The C antigen positivity was only in 2 (66.6%) individuals in the DEL positive group and 178 (90.3%) in the DEL negative samples. All the three samples which were found to be positive as DEL phenotype also gave negative result for DAT, Weak D testing and Auto Control.

Conclusion: The frequency of DEL phenotype in north Indian RhD negative donor population is 1.5%.