Hematological Characteristics of Hb Constant Spring (HBA2: c.427T>C) Carriers in Mainland China

Hb Constant Spring (Hb CS) (HBA2: c.427T>C) is a common α-globin variant causing α-thalassemia (α-thal) phenotypes in mainland China. In this study, we evaluated the efficiency of erythrocyte parameters and capillary electrophoresis (CE) in the determination of Hb CS in blood samples from Hb CS carriers. Based on molecular diagnosis, there were 462 patients carrying Hb CS: 411 Hb CS heterozygotes, seven carried Hb H-Hb CS disease, 18 compound heterozygotes for Hb CS/α⁺-thal, and 26 double heterozygotes for Hb CS and β-thalassemia (β-thal). Forty-three cases had no Hb CS peak visible on CE, including all 26 cases of double heterozygotes for Hb CS and β-thal, and 17 cases of heterozygotes carrying only Hb CS. Hb CS heterozygotes, those without a Hb CS peak, presented with lower hemoglobin (Hb), mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) values than those with a Hb CS peak. The MCV <80.0 fL yielded a detection rate of 87.8% for screening individuals carrying Hb CS. Therefore, we emphasize that if one partner of a couple has tested positive for α⁰-thal, the other should be subjected to detailed screening for this nondeletional allele using molecular analysis, regardless of his/her red cell indices and electrophoretic chromatogram.