Diagnosis of a-thalassaemia trait from Coulter Counter 'S' indices

A number of patients of Mediterranean and Asian origins were found to have unexplained microcytic hypochromic red blood cells. Iron deficiency and fl-thalassaemia trait were both satisfactorily excluded in all of them. The haematological indices of these patients, obtained on a Coulter Model 'S' Counter, were found to be very similar to those seen in obligatory heterozygotes for oc-thalassaemia. It is postulated that these patients were also carriers for oc-thalassaemia. Subsequent investigation of some of these patients showed the characteristically reduced rates of cxchain synthesis seen in this condition. The discriminant function of England and Fraser (1973) may be of help in diagnosing this state. cx-Thalassaemia trait should be considered in all patients of 'highrisk' ethnic origins with a blood picture suggestive of /3-thalassaemia trait but in whom the levels of Hb A2 and Hb F are within normal limits.