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

Abstract

alpha-Thalassemia is prevalent among Asian-Americans. Most cases involve deletions of one or more alpha-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 alpha-thalassemia. The purpose of this study was to determine both the frequency of alpha-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; -alpha3.7; 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 alpha-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, -alpha3.7, and --FIL.