[Screening for alpha-thalassemia using DNA analysis].

alpha-thalassemia was sought by gene mapping in 258 subjects selected on the basis of origin (25%), microcytosis (7%), or origin and microcytosis combined (64%). Abnormal fragments (Xba I/probe alpha) were found in 58 cases (22.5%). Using other restriction enzymes it was possible to determine the genotype alpha-/aa in 39 patients and the genotype alpha-/alpha- in 13 patients; 2 patients also exhibited hemoglobin H (alpha-/--) disease. alpha triplication anti-3.7 kb was found in 2 subjects and zeta-thalassemia in 2 other samples. 57 out of 58 patients originated from the thalassemia belt or from Africa. alpha-thalassemia is the most frequent hemoglobinopathy (21% of patients at risk) and hematologically is characterized by microcytosis. The Hb A2 level is decreased only in the alpha-/-- form of the disease. The main advantage of diagnosing zeta-thalassemias and alpha triplications lies in the possible clinical implications in the event of association with other hemoglobinopathies or beta-thalassemia.