Screening for common nondeletional α-thalassemias in Chinese newborns by determination of Hb Bart's using the Sebia Capillarys 2 electrophoresis system.

The interaction of the nondeletional α-thalassemia (α-thal) mutations with the Southeast Asian double α-globin gene deletion results in nondeletional Hb H (β4) disease. Hb Constant Spring (Hb CS, α142, TAA>CAA at α2) and Hb Quong Sze [Hb QS, α125, CTG>CCG (α2)] are the most common nondeletional α-thalassemias in the Chinese population. These α-globin structural variants are unstable and undetectable by routine hemoglobin (Hb) electrophoresis. The amount of Hb Bart's (γ4) in the cord blood of newborns correlates with the number of α-globin genes that are deleted. We determined the quantity of Hb Bart's in cord blood at birth with the Sebia CapillaryS electrophoresis system. Using Hb Bart's levels at 0.1-2.5% as a cut-off range for nondeletional α-thal diagnosis, we detected 154 individuals in 6,525 newborns. Of the 154 samples, 12 were found to be Hb CS carriers, 10 Hb QS carriers, and one Hb Westmead [α122, CAC>CAG (α2)] carrier. We present the first report of the prevalence of Hb QS in our population.