Background and Aims: A pilot screening program for thalassemia was initiated in the Lao People's Democratic Republic. This study aimed to describe the genotype diversity and hematologic features of thalassemia among the participating pregnant women. Methods: Blood samples of 411 pregnant Laotian women were collected. Hemoglobin (Hb) profiles were determined using a capillary zone electrophoresis system. Mutations of α- and β-globin genes were investigated using a polymerase chain reaction and related techniques. Results: As many as 26 different thalassemia genotypes including non-transfusion-dependent thalassemia, i.e. Hb E-β-thalassemia, Hb H, and EA Bart's diseases, were identified. A variety of phenotypic expressions of hematologic features and Hb profiles were observed, including an unusual phenotype of Hb E-β⁰ thalassemia with 89.1% Hb E, 1.6% Hb F, and 9.3% Hb A2. Conclusions: The remarkable genotype-phenotype diversity indicates a need for careful laboratory interpretation in order to provide appropriate genetic counseling and care to the Laotian population.

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