FREQUENCY OF DELETIONAL ALPHA-THALASSEMIA GENOTYPES IN A PREDOMINANTLY ASIAN-AMERICAN POPULATION

alpha-Thalassemia is prevalent among Asian-Americans. Most cases invol ve deletions of one or more alpha-globin genes. Parents with two-gene cis deletions can have offspring with hemoglobin Bart's hydrops fetali s or hemoglobin H disease. The diversity of deletions poses special ch allenges to laboratories that offer DNA-based testing for alpha-thalas semia. The purpose of this study was to determine both the frequency o f alpha-thalassemia genotypes in a predominantly Asian-American popula tion (n = 78) and the mutation detection rate of a comprehensive South ern blot method. The ethnic composition of the study population was si milar to the major Asian-American groups that reside in the United Sta tes as a whole. Three mutations (the Southeast Asian type, --SEA; -alp ha(3.7); and the Filipino type, --FIL) accounted for all mutant allele s present in the Asian-American patients tested for reproductive reaso ns. The relative frequencies of these three mutations were 62%, 27%, a nd 11%, respectively. The mutation detection rate was 100%. Laboratori es that perform DNA-based alpha-thalassemia testing in populations sim ilar to the one residing in Washington State should use a testing syst em that allows for the unequivocal identification of the haplotypes de tected in the study population, namely --SEA, -alpha(3.7), and --FIL.