RESUMO
The alpha thalassaemias are common genetic disorders that arise from reduced synthesis of the alpha globin chains. At present, large scale carrier screening and clinically valuable antenatal detection programs have not been established for the congenital disorder alpha thalassaemia. This study was conducted on 410 umbilical cord blood samples to detect the relative frequency and differentiate between the five common alpha thalassaemia deletional forms, regardless of the break points, among a group of Egyptian neonates using a single tube multiplex-PCR assay. The method proved to be simple, easy and fast as the number of alpha genes present in the subjects were directly determined by the number and intensity of the alpha l and alpha 2 bands normalized with that of beta actin [serving as an internal control]. A complete blood picture was done for all samples. Among the DNA samples tested, ten cases were discarded due to failure of amplification. Our results showed that 38 samples [9.5%] were identified as carriers of alpha thalassaemia or suffering from Hb H disease. The percentage of the different genotypes detected was: 4.5% alpha thalassaemia 2 heterozygous [-alpha/ alpha alpha], 3% alpha thalassaemia 2 homozygous [-alpha /-alpha], 1.75% alpha thalassaemia 1 heterozygous [--/alpha alpha] and 0.25% Hb H disease [--/-alpha]. No cases of Hb B art's hydrops fetalis were detected. On comparing the hematological profile of the normal subjects with that of those with gene deletions it was found that alpha thalassaemia carriers had significantly lower Hb levels, Hct%, MCH and MCHC while the MCV did not differ markedly. No statistically significant difference was found between the various genotypes detected regarding their blood indices. From this we can not rely upon blood indices only for detection of alpha thalassaemia and we highlight the importance of molecular diagnosis using this simple single tube PCR assay in diagnosis of alpha thalassaemia carriers