Real-time quantitative PCR analysis for alpha-thalassemia-1 of Southeast Asian type deletion in Taiwan

Since homozygosity of the alpha-thalassemia-1 of Southeast Asian (SEA) type deletion results in hydrops fetalis, a novel protocol based on the real-time quantitating polymerase chain reaction (PCR) technique has been developed to quantify the intact and aberrant alpha-globin genes in adults. The ratio of the normal/SEA-bearing alpha-globin genes was expressed in cycle threshold (C(T)) values. Theoretically, a relative ratio of one to one was anticipated in individuals carrying the SEA type deletion. Twenty-five heterozygous and 20 normal cases were analyzed retrospectively with this protocol. Data showed that the CT values for the intact alpha-globin gene allele and the allele bearing the SEA type deletion in carriers were 28.74+/-1.49 and 26.46+/-2.05, respectively. Therefore, the ratio of normal/SEA type deletion-bearing alpha-globin genes in the carriers was 1.09+/-0.043. No ambiguous results were observed from other less common genotypes associated with alpha-thalassemia, such as the Philippine type deletion. Based on the results, we concluded that this protocol could provide a rapid method to mass screen carriers with alpha-thalassemia-1 of SEA type deletion in this region.