Frequency of deletional α-thalassemia genotypes in a predominantly Asian-American population

Abstract

α-Thalassemia is prevalent among Asian-Americans. Most cases involve deletions of one or more α-globin genes. Parents with two-gene cis deletions can have offspring with hemoglobin Bart's hydrops fetalis or hemoglobin H disease. The diversity of deletions poses special challenges to laboratories that offer DNA-based testing for α-thalassemia.The purpose of this study was to determine both the frequency of α-thalassemia genotypes in a predominantly Asian-American population (n = 78) and the mutation detection rate of a comprehensive Southern blot method. The ethnic composition of the study population was similar to the major Asian-American groups that reside in the United States as a whole. Three mutations (the Southeast Asian type, - SEA; -α3.7; and the Filipino type, -FIL) accounted for all mutant alleles present in the Asian-American patients tested for reproductive reasons. The relative frequencies of these three mutations were 62%, 27%, and 11%, respectively. The mutation detection rate was 100%. Laboratories that perform DNA-based α-thalassemia testing in populations similar to the one residing in Washington State should use a testing system that allows for the unequivocal identification of the haplotypes detected in the study population, namely - -SEA, -α3.7 and -FIL.