Incidence of Hb Constant Spring and Hb Paksé in Khon Kaen province: Examination using capillary electrophoresis and DNA analysis

Abstract

Hemoglobin Constant Spring (Hb CS) and Hb Paksé are the two common abnormal Hbs causing non-deletional α-thalassemia 2 in Thailand.  Hb analysis could not separate them. Both are unstable; their levels in peripheral blood are so small that they could be undetected in routine setting. To update recent information of the two Hbs in population, the incidences of Hb Constant Spring and Hb Paksé were re-examined using capillary electrophoresis and multiplex allele specific PCR. Three hundred and forty cord blood specimens anticoagulated with EDTA were consecutively collected from newborns delivered at the Health Promotion Center Region 6, Khon Kaen province during January - May 2012. Among these, we identified 17 cases (5.0 %) with Hb CS and 5 cases (1.5 %) with Hb Paksé, including 11 heterozygous Hb CS, 1 double heterozygous Hb CS / Hb E, 1 compound heterozygous Hb CS / a-thal 2 (3.7 kb deletion), 3 compound heterozygous Hb CS / a-thal 2 (3.7 kb deletion) with heterozygous Hb E , 1 compound heterozygous Hb CS / a-thal 2 (3.7 kb deletion) with homozygous Hb E, 2 heterozygous Hb Paksé, 3 double heterozygous Hb Paksé - Hb E. The gene frequencies for Hb CS and Hb Pakse’ were 0.025 and 0.007 respectively. It was found that among these 22 cases with Hb CS and Hb Paksé genes, small peaks at zone 2 on capillary electrophoresis were detected in only 5 of them. The result in this study indicates high incidences and heterogeneity of the two Hbs in northeast Thai population. Diagnosis made by Hb analysis was not sufficient, requiring further DNA analysis. Moreover, data demonstrates that approximately 22.7 % of diagnosis of Hb CS based on a small peak of Hb in zone 2 of the routine capillary electrophoresis could alternatively be Hb Paksé in this population. The results from this study should prove useful in genetic counseling and facilitating a prevention and control program of thalassemia in the region.