Percentile curves for red cell indices of 413-1413-1413-1heterozygotes in infancy and childhood

Abstract

This paper describes the percentile curves for red blood cell (RBC) count, Hb, mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) values of β^°-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 parallelling 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 α-thalassaemia in the Sardinian population, to which all the subjects investigated belong, the 3^rd MCH-MCV percentile curves of normal overlap the 97^th curve of β-thalassaemia heterozygotes. The HbA₂ levels, however, were always increased as compared to normal. These results confirm in children than screening for heterozygous β-thalassaemia in populations with a high incidence of α and β-thalassaemia by MCV-MCH determination may overlook a sizeable proportion of β-thalassaemia carriers. The knowledge of the extent of variation of RBC indices of β-thalassaemia heterozygotes during infancy, childhood and adolescence, is very useful for the evaluation of a child presenting with a mild microcytic anaemia.