Screening for alpha-thalassemia. Correlation of hemoglobin H inclusion bodies with DNA-determined genotype.

We evaluated potential screening protocols for alpha-thalassemia in a group of 80 patients whose genotypes were determined by Southern blot analysis with alpha- and zeta-globin DNA probes. Erythrocyte inclusion bodies were measured by a modified brilliant cresyl blue test. Erythrocyte indices and iron status were also measured. The brilliant cresyl blue test reliably detects couples at risk for hemoglobin Bart's hydrops fetalis. Measurement of the number of inclusion bodies differentiates the alpha-thalassemia genotypes in the absence of a coincident beta-chain synthesis deficiency, such as hemoglobin E or beta-thalassemia. The test appears to identify patients, such as those with the Thai and Filipino deletion variants, whose alpha-thalassemia cannot be definitively characterized by DNA testing when only alpha- and zeta-globin probes are used in the analysis. We also found evidence of elevated serum ferritin levels in many patients with deletion of two or three alpha-globin genes. This study shows that most routine screening for alpha-thalassemia can be performed with three simple tests: (1) the brilliant cresyl blue inclusion study, (2) erythrocyte indices, and (3) iron studies. Analysis with DNA probes is needed in only some circumstances.