Frequency of delta(+)27-thalassaemia in Sardinians

To determine the incidence of delta(+)27 thalassaemia in Northern Sardinia we examined blood samples from 750 Sardinian schoolboys by PCR-based molecular analysis. The incidence of delta(+)27 mutation was 1.2% in this study, i.e, twice as high as previously described on the basis of phenotypical studies; the frequency of the beta-thalassaemia is 10.5% and their interaction has been calculated at 0.0003. The majority of delta(+)27 carriers are characterized by a HbA(2) level lower than 1.9% and the mean HbA(2) level is significantly lower than in normal subjects. All compound heterozygotes for delta(+)27 and beta-thalassaemia show a silent beta-thalassaemic phenotype related to normalization of their HbA(2) levels. This study suggests that delta(+)27 thalassaemia should be borne in mind in counselling at-risk couples in which one member has the typical high HbA(2) beta-thal trait while the other shows normal or borderline HbA(2) level. In these subjects, PCR-based ECO O 109 I digestion of the delta globin gene allows rapid detection of the delta(+)27 mutation.