Comparison of methodologies for thalassemia screening by Hb A2 quantitation.

An efficient, reliable, inexpensive screening test for beta-thalassemia triat is required before the National Cooley's Anemia Control Act can be carried out. Densitometry of hemoglobin samples separated by cellulose acetate has become a routine procedure to quantitate Hb A2 and thereby indicate beta-thalassemia trait carriers. To determine the utility of densitometry in quantitation of Hb A2, we evaluated three densitometers marketed in the United States. Individuals with genetically proved beta-thalassemia trait and normal Hb AA controls were studied. Two analytic procedures (elution and column chromatography) for Hb A2 quantitation were used as reference methods. Densitometry was shown to be unsatisfactory for detecting beta-thalassemia-trait carriers. We recommend that a unified approach to the detection of anemia, which would include thalassemia trait, be developed in the United States rather than free-standing thalassemia screening centers and clinics.