Percentile curves for red cell indices of beta zero-thalassaemia heterozygotes in infancy and childhood.

This paper describes the percentile curves for red blood cell (RBC) count, Hb, mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) values of beta zero-thalassaemia heterozygotes during infancy, childhood and adolescence. Hb values were about 2 g/dl below those of normal controls with a progressive increase with age paralleling the normal developmental trend. The Hb increase with age was due to a progressive rise in the Hb content per cell, the number of RBC remaining nearly constant. MCV and MCH values also increased with age with a pattern parallel to normal control. Because of the high prevalence of alpha-thalassaemia in the Sardinian population, to which all the subjects investigated belong, the 3rd MCH-MCV percentile curves of normal overlap the 97th curve of beta-thalassaemia heterozygotes. The HbA2 levels, however, were always increased as compared to normal. These results confirm in children than screening for heterozygous beta-thalassaemia in populations with a high incidence of alpha and beta-thalassaemia by MCV-MCH determination may overlook a sizeable proportion of beta-thalassaemia carriers. The knowledge of the extent of variation of RBC indices of beta-thalassaemia heterozygotes during infancy, childhood and adolescence, is very useful for the evaluation of a child presenting with a mild microcytic anaemia.