Hemoglobin constant spring in bangkok: Molecular screening by selective enzymatic amplification of the α<inf>2</inf>‐globin gene

Abstract

Hemoglobin Constant Spring (Hb CS) is a hemoglobin variant with an elongated α‐globin chain secondary to a chain termination mutation. The diagnosis of HbCS by electrophoresis is difficult because it is present in very low amounts in the red cells of heterozygotes. Selective enzymatic amplification of the α2‐globin gene and allele‐specific hybridization for Hb CS gene provided accurate diagnosis of Hb Constant Spring. We have used this approach to detect the αcs mutation in the cord blood that contained all four α‐globin genes but had Hb Bart on electrophoresis. The αcs mutation was found in six subjects whose Hb Bart levels were 3.0, 3.2, 3.7, 4.0, 4.9, and 9.8%. The latter also had −α mutation on the other chromosome, giving rise to the genotype αcsα/−α, which produced high Hb Bart. The gene frequency for αcs in the Thai calculated from a total of 406 cord blood studied in Bangkok was found to be ∼0.008. Copyright © 1991 Wiley‐Liss, Inc., A Wiley Company