Molecular basis and hematologic characterization of deltabeta-thalassemia and hereditary persistence of fetal hemoglobin in Thailand.

Background and Objectives: Hereditary persistence of fetal hemoglobin (HPFH) and deltabeta-thalassemia are heterogeneous disorders characterized by increased levels of Hb F in adult life. The distinction between these two conditions is not always possible from routine hematologic analyses. This study investigated the hematologic and molecular characteristics of high HbF determinants in Thailand, and describes a rapid DNA-based assay to facilitate diagnosis in a routine laboratory.
Design and Methods: A multiplex allele-specific polymerase chain reaction (PCR) system for rapid detection of three common DNA deletions causing (deltabeta)0-thalassemia and HPFH in South-east Asians was developed and used to examine the molecular basis for the high Hb F phenotypes in 273 unrelated Thai individuals. Hematologic data were recorded and correlated to the molecular findings.
Results: The multiplex PCR system was validated and results were completely concordant with those of other established methods. DNA analysis identified GgAg(deltabeta)0-thalassemia in 148 cases (54.2%), deletional HPFH-6 in 83 (30.4 %) and the deletion-inversion Ggamma(Agammadeltabeta)0-thalassemia in 22 (8.1 %) cases, while another 20 (7.3 %) subjects remained uncharacterized. Genotype-phenotype relationships are discussed.
Interpretation and Conclusions: These data emphasize the high frequencies of deltabeta-thalassemia and HPFH in Thailand and the need for differential diagnostic methods since the hematologic parameters associated with the conditions are very similar and overlap. The multiplex allele-specific PCR approach should prove useful in complementing routine Hb analysis for the differential diagnosis of these three common causes of high Hb F determinants and should facilitate a program of hemoglobinopathy screening in the region.