Geographic boundary for the Asian-type DEL in south Asia.

Red cells with the Del phenotype test as D negative. Del is common among D-negative individuals in east and southeast Asia. Practically, all of them are caused by the RHD c.1227G>A variant, called Asian-type DEL, which has never been reported in south Asia. Among 56,445 blood donors in the east Indian state of West Bengal, 2,422 D-negative samples were identified (4.3%), of whom 195 were positive for the C or the E antigen. Using adsorption/elution, we found one Del, not caused by Asian-type DEL. Red cell genotyping revealed hybrid RHD-CE-D genes in 16 donors. Our data from east India established a geographic boundary for the Asian-type DEL west of Myanmar. The Asian-type DEL is absent from India. These findings showed that RHD genetics differ across Asia in ways relevant to transfusion practice. Transfusion strategies in India can align with those used in western populations rather than east Asian populations.