Comparison of the hematological parameters among different β-thalassemia mutations revealed an increasing trend of MCV and MCH in a group of heterozygous states for the 3.4kb deletion and the A-G substitution at nucleotide (NT) -28.
Appropriate cut-off values of MCV and MCH for screening of α(0) and β thalassemias were derived from the receiver operator characteristic curve conducted initially on 279 subjects with various thalassemia genotypes.
The propositus was a 39-year-old female and noted to be heterozygous for beta-thalassemia with hemoglobin (Hb) level of 10.1 g/dl, MCV 70 fl, MCH 23.1 pg, HbA2 6.3%, and HbF 2.4%.
The mean hemoglobin (Hb) concentration, MCV, and MCH were significantly (p < 0.0001) lower in patients with beta-thalassemia traits (BTT) who had iron deficiency than in those without iron deficiency.
Excluding two cases with HbA2 levels within the range of the beta-thalassemia carrier state, heterozygotes for this mutation showed normal or borderline red blood cells count, Hb levels, MCV, MCH and HbA2 values, and unbalanced globin chain synthesis.
The cause of the hypochromia in subjects with a normal Hb A2 (30% of the total population) is probably alpha thalassaemia, firstly because in those patients with an MCH of 19-24 pg the other haematological parameters are statistically the same as those with proven beta thalassaemia and, secondly, in those with an MCH of 25-27 pg iron deficiency is not common (6% of the population).
Variation in haematological data, mainly MCV and MCH values, was found to be caused in part by the type of beta-thalassaemia (defined by its haplotype) and by the presence of an additional alpha-thalassaemia-2 heterozygosity or homozygosity.
Individual values for MCV, MCH and Hb A2 in the beta+ type occasionally overlapped those in the normal population casting doubt on the adequacy of these criteria in identifying all cases of heterozygous beta+ thalassaemia.