Incidence of ABO(H) blood group variants among the Bulgarian population.

The result of a screening of ABO (Hh) variants after investigating the blood group of 106,980 persons are presented. The Ax variant is registered most frequently among the Bulgarian population. As a whole the frequencies of ABO blood group variants Ax, Ael, A3, Aend and Am among the Bulgarian population are similar to that established by other authors among the French population and nearly twice as high as among the population of Bombay. The group of H-deficient phenotypes includes AA1Xh, AHm, OHm variants. Their frequency is significantly lower when compared with the frequency of AHm and OHm variants among the population of Thailand. Variants A1 and Aint with unusually high H-content are classified as A1H, A1Hint, Aint H and integrated as a category of H-excess phenotypes. Their incidence among the Bulgarian population is significantly lower than that registered among Maharastrian, South African Bantu and Indian.