Screening for thalassaemia and/or iron deficiency: evaluation of some discrimination functions.

The number concentration of erythrocytes in blood (RBC) and the discrimination functions MCV/RBC, (MCV)2 X MCH, DF = (MCV/fl) - (RBC/10(12).1(-1] - (8.1 X Hb mmol.1(-1] - 3.4 have been advocated as useful methods in screening programmes for thalassaemia. In the present work we attempted to estimate the value of each of these methods in screening programmes for thalassaemia and/or iron deficiency and in differentiating between these two conditions. One hundred and twenty-six subjects suffering either from iron deficiency anaemia or heterozygous beta, delta beta, 'silent' beta and alpha 1 thalassaemia were classified by using these methods. Forty healthy subjects served as controls. The RBC was greater than 5.5 X 10(12)1(-1) in 80% of the cases, the three discrimination functions were 'positive' in 91%, 94% and 92% respectively. MCV/RBC and (MCV)2 X MCH separated successfully the subjects with microcytic anaemia (heterozygous thalassaemia and iron deficiency) from normal controls. On the other hand the DF turned out to be more satisfactory than RBC in discriminating heterozygous thalassaemia from iron deficiency anaemia. Thus in population screening for thalassaemia either MCV/RBC or (MCV)2 X MCH ought to be used first and then the DF.