Abstract
Elevated Hb A2 level (≥4.0%) is considered to be reliable parameter to identify β-thalassemia (β-thal) carriers. However, some β-thal carriers have been misdiagnosed as their Hb A2 levels are below 4.0%. In addition, coinheritance of α-thalassemia (α-thal) and β-thal might affect Hb A2 levels. Therefore, the aim of this study was to investigate the mutations of β- and α-globin genes in individuals with borderline Hb A2 levels in Thailand. Three hundred samples from individuals with Hb A2 levels of 3.5–3.9% were collected for molecular diagnosis of β-globin gene mutations. In addition, the α0-thal, α+-thal, Hb Constant Spring (Hb CS, HBA2: c.427T>C), and Hb Paksé (HBA2: c.429A>T) diagnostics were also performed. Sixteen samples (5.33%) had β-globin gene mutations, and codon 41/42 (–TTCT) (HBB: c.126_129delCTTT) was the most prevalent mutation. Ninety-eight samples (32.67%) had α-globin gene mutations including four Hb H (β4)-Hb CS disease, two Hb H disease, 13 heterozygous α0-thal, 11 homozygous α+-thal, two α+-thal/Hb CS, one α+-thal/Hb Paksé, 61 heterozygous α+-thal, and four Hb CS. Furthermore, seven cases of β-thal carriers coinheriting α-thal were observed, and five of them carried Hb H disease. High prevalence of both α- and β-thal in subjects with borderline Hb A2 levels suggested that molecular diagnosis of α- and β-thal should be performed, especially in a high prevalence area of thalasssemia carriers, for accurate diagnosis and genetic counseling to prevent and control new severe thalassemia cases. Moreover, β-thal carriers who coinherited Hb H disease might have reduced Hb A2 levels, leading to a misdiagnosis of β-thal in analysis programs.
Acknowledgments
We would like to thank the technicians at the Associated Medical Sciences Clinical Service Center (AMS-CSC), Chiang Mai University, Chiang Mai, Thailand for their assistance. The authors thank Mrs. Kallayanee Treesuwan and Dr. Panthong Singboottra Myers, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand, for refinement of the English language.
Disclosure statement
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.