Prevalence of elevated hemoglobin A2 measured by the CAPILLARYS system.

Hemoglobin (Hb) A2 electrophoresis has been used for prenatal screening for the beta-thalassemia trait (betaTT). We retrospectively reviewed Hb capillary electrophoresis performed in our laboratory. We found that of the 122 cases showing elevated HbA2 levels, 79 cases were due to hemoglobinopathies, mostly HbS. Review of the RBC indices suggested that 3 of 36 cases with elevation of HbA2 in the HbAA-pregnancy group had betaTT and 29 had normal RBC indices; data were not available for 4 patients. Among 7 cases with elevation of HbA2 in the HbAA-other group, 5 had betaTT and 2 were normal. The number of patients without betaTT but with HbA2 elevation in the pregnant group was significantly higher than that in the nonpregnant group. When a higher HbA2 cutoff (3.5%) was used, only 3 pregnant patients without betaTT had HbA2 elevation, similar to the nonpregnant group. We found that a significant number of pregnant women with mild HbA2 elevation had no evidence of betaTT, compared with the nonpregnant group.