Immunologic diagnosis of alpha-thalassemia traits.

Frequently it is impossible to diagnose alpha-thalassemia-2 trait from hematologic findings, since the red cell morphology and the MCV are normal. In such cases, after the neonatal period Hb Bart's is not detectable by conventional electrophoreses and chromatography. Antibody against Hb Bart's was produced in rabbits by repeated injections with Hb Bart's from Hb Bart's hydropic fetuses. The antibody was specific for Hb Bart's without crossreaction with Hbs A, A2, E, F and H. By the capillary tube precipitin test Hb Bart's was demonstrable in 82% of 87 obligatory cases for alpha-thalassemia traits, 86% in alpha-thalassemia-1 trait and 79% in alpha-thalassemia-2 trait. The test was positive in 21% of the general subjects, corresponding to the prevalence of alpha-thalassemia in Bangkok. Thus the immunologic demonstration of Hb Bart's appears to offer a diagnostic screening test for alpha-thalassemia traits in the postneonatal period.