RESUMO
BACKGROUND: The aim of this study was to establish a sensitive method that can detect the presence of not only the common but also the unusual or unknown α-globin gene deletions for screening of α-thalassemia. We used quantitative multiplex PCR of short fluorescent fragments (QMPSF) for the α-globin genes (HBA) to screen α-thalassemia deletions. METHODS: We set up and validated HBA-QMPSF using 50 negative and 100 positive controls of deletional α-thalassemia. To evaluate its ability to detect the presence of the common and unusual or unknown α-globin gene deletions, 579 unrelated samples were simultaneously analyzed using this assay and multiplex Gap polymerase chain reaction (Gap-PCR). The inconsistent results were further confirmed by multiplex ligation-dependent probe amplification (MLPA). RESULTS: HBA-QMPSF was capable of detecting α-globin gene deletions with an acceptable variability as shown by mean values (SD) of allele dosage for the heterozygous deleted control obtained from intra- and inter-experimental replicates [0.63 (0.01) and 0.61 (0.03)]. In 572 out of the 579 unrelated subjects, HBA-QMPSF and multiplex Gap-PCR gave consistent results. In seven cases which were finally proved to be composed of one rare deletion--Thai/-α3.7, one novel deletion--SEA/-α2.8, four αααanti3.7/αα and one αααanti4.2/αα triplications, HBA-QMPSF showed deletion or duplication in the α-globin gene while multiplex Gap-PCR failed to give the correct diagnosis. CONCLUSIONS: HBA-QMPSF is able to detect the presence of the common and unusual or unknown α-thalassemia deletions and duplications. It can be used as an initial screening test for α-thalassemia caused by HBA gene copy number alteration.