Diagnosis of α0-thalassemia Chiang Rai (--CR) deletion by melt curve analysis in Northern Thailand.

A large novel 44.6 kb deletion named α0-thalassemia Chiang Rai (--CR) was first described in the individuals with uncommon Hb Bart's hydrops fetalis and HbH disease. This study aimed to develop a real-time gap PCR and melt curve analysis for the detection of --CR and investigate its frequency in northern Thailand. Among 4,952 blood samples, the assay was performed in 525 samples with a mean corpuscular volume (MCV) < 80 fL, HbA2 < 3.5%, HbA2+E < 25%, and negative for common deletional α0-thalassemia --SEA and --THAI. The developed method showed Tm values of 85.8 ± 0.0 °C and 91.5 ± 0.1 °C, which were specific for --CR and wild-type alleles, respectively. Nine (0.18% of 4,952 or 1.71% of 525) were positive for --CR, in which two were HbH disease and the rest were heterozygous for --CR. This study demonstrated the success of real-time gap PCR with melt curve analysis for --CR diagnosis. Additionally, the prevalence of --CR in the northern Thai population was comparable to --THAI. Thus, this study implies the importance of --CR in northern Thailand. Moreover, the developed real-time gap PCR with melt curve analysis is simple and highly accurate, and may be considered as an additional tool for routine α0-thalassemia --CR diagnosis in this region.