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

Abstract

A number of patients of Mediterranean and Asian origins were found to have unexplained microcytic hypochromic red blood cells. Iron deficiency and β-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 α-thalassaemia. It is postulated that these patients were also carriers for α-thalassaemia. Subsequent investigation of some of these patients showed the characteristically reduced rates of α-chain synthesis seen in this condition. The discriminant function of England and Fraser (1973) may be of help in diagnosing this state. α-Thalassaemia trait should be considered in all patients of 'high-risk' ethnic origins with blood picture suggestive of β-thalassaemia trait but in whom the levels of Hb A2 and Hb F are within normal limits.