Prospective screening for δ-hemoglobinopathies associated with decreased hemoglobin A2 levels or hemoglobin A2 variants: A single center experience.

ABSTRACT

BACKGROUND: δ-hemoglobinopathies may lead to misdiagnosis of several thalassemia syndromes especially ß-thalassaemia carrier, it is important to evaluate the δ-globin gene defects in areas with high prevalence of globin gene disorders. We describe a prospective screening for δ-hemoglobinopathies in a routine setting in Thailand. METHODS: Study was done on a cohort of 8,471 subjects referred for thalassemia screening, 317 (3.7%) were suspected of having δ-globin gene defects due to reduced hemoglobin (Hb) A2 levels and/or appearance of Hb A2-variants on hemoglobin analysis. Hematologic and DNA analysis by PCR and related assays were carried out. RESULTS: DNA analysis of δ-globin gene identified seven different δ-globin mutations in 24 of 317 subjects (7.6%). Both known mutations; δ-77(T>C) (n = 3), δ-68(C>T) (n = 1), δ-44(G>A) (n = 8), Hb A2-Melbourne (n = 5), δIVSII-897(A>C) (n = 5), and Hb A2-Troodos (n = 1) and a novel mutation; the Hb A2-Roi-Et (n = 1) were identified. This Hb A2-Roi-Et, results from a double mutations in-cis, δCD82(AAG>AAT) and δCD133(GTG>ATG), was interestingly found in combination with an in trans, 12.6 kb deletional δß0-thalassemia in an adult Thai woman who had no Hb A2 and elevated Hb F. A multiplex-allele-specific PCR was developed to detect these novel δ-globin gene defects. CONCLUSIONS: The result confirms a diverse heterogeneity of δ-hemoglobinopathies in Thailand which should prove useful in a prevention and control program of thalassemia in the region.