Comparison of Haematological Features of the β0and β+Thalassaemia Traits in Jamaican Negroes

Abstract

Hematological characteristics were compared in 29 subjects with heterozygous .beta.0 thalassemia and in 33 subjects with heterozygous .beta.+ thalassemia, identified by the type of sickle cell-.beta. thalassemia among close relatives, in a Jamaican Negro population. Total hemoglobin, MCV [mean corpuscular volume] and MCH [mean corpuscular Hb] were significantly lower in the .beta.0 type but the level of Hb A2 was not significantly different. Individual values for MCV, MCH and Hb A2 in the .beta.+ type occasionally overlapped those in the normal population casting doubt on the adequacy of these criteria in identifying all cases of heterozygous .beta.+ thalassemia. The hematological differences are those which would be expected on theoretical grounds. The inability to confidently differentiate the 2 types of heterozygous .beta. thalassemia has implications for genetic couseling. The inability to distinguish heterozygous .beta.+ thalassemia from normals on any single hematological index suggests that surveys depending on estimations of Hb A2 or on MCV alone may have underestimated the prevalence of the .beta.+ thalassemia gene.