Osmotic fragility test in heterozygotes for alpha and beta thalassaemia.

This study shows that the combination of heterozygous beta thalassaemia and deletion heterozygous (-alpha/alpha alpha) or homozygous (-alpha/-alpha) alpha+ thalassaemia may result in the production of erythrocytes which have normal mean volume and haemoglobinisation but decreased osmotic fragility. Based on this finding and previous studies, which have shown that beta thalassaemia screening by the osmotic fragility test may miss a significant proportion of beta thalassaemia heterozygotes, we conclude that beta thalassaemia screening in a population in which both alpha and beta thalassaemia are prevalent should combine the one tube osmotic fragility test with electronic measurement of red blood cell indices in the initial screening process.