Detection of ζ‐globin chains in the cord blood by ELISA (enzyme‐linked immunosorbent assay): Rapid screening for α‐thalassemia 1 (Southeast Asian type)

Fetuses with homozygous α‐thalassemia 1, in which the deletion of all four α‐globin genes results in the absence of any α‐globin chains, are severely anemic with clinical features of hydrops fetalis. Definitive diagnosis of α‐thalassemia 1 carriers is difficult since there are few red cell abnormalities. Recently Chui et al. found that minute amounts of embryonic ζ‐globin chains are present in adult hemoglobin of the Southeast Asian type of α‐thalassemia 1 carriers. In this study, we screened 521 cord bloods for α‐thalassemia 1. Hemoglobin analysis, including quantitation of Hb Bart's, was performed using the automated HPLC, α‐thalassemia short program (VARIANT, Bio‐Rad, Hercules, CA). Of these, 200 cord blood samples in which Hb Bart's was demonstrated were tested for the presence of ζ‐globin chains by ELISA using labeled anti‐ζ monoclonal antibody. ζ‐Globin ranged between 0.21 and 0.83% in 19 specimens carrying α‐thalassemia 1 gene. In the remaining 90 out of 109 specimens in which Hb Bart's was greater than 1.2%, ζ‐globin was less than 0.17%. DNA analysis revealed the presence of normal α‐genotype and other types of α‐thalassemia including α‐thalassemia 2 and Hb Constant Spring. One false positive was found in which the ζ‐globin was 0.25% by ELISA but in which PCR indicated an α‐thalassemia 2 heterozygote. Ninety‐one samples with Hb Bart's of less than 1.2% by HPLC are most likely normal with a ζ‐globin range between 0 and 0.14%. This study also showed that the frequency of α‐thalassemia 1 in Bangkok is 3.65%. Am. J. Hematol. 57:283–286, 1998. © 1998 Wiley‐Liss, Inc.