Analysis of Distribution of Thalassemic Genotype and Clinical Phenotype

ObjectiveTo determine the incidence of Thalassemia, the distribution of Thalassemic genotype and clinical phenotype.MethodsReverse dot blot (RDB) hybridization was used to detect the common three α-globin gene deletions(−SEA, -α3.7 and -α4.2) by Gap-PCR over all 8 118 cases and to detect 17 β-globin gene 17 mutations (CD41-42, IVS- II −654, CD17, −28, βE, CD71−72, CD27−28, −29, CD43, CD14−15, IVS-I−1, IVS-I−5, CAP, −31, Int, −32, −30) among 7 934 cases. Patients were grouped according to clinical phenotype such as anemia symptom, screening test of thalassemia and family carrier history.ResultsAmong 8 118 cases, there were 2 519 cases with α-globin gene deletions over 9 kinds genotypes, and the incidence of α-thal was 31.03%. The genotypes of –SEA/αα, -α3.7/αα, -α4.2/αα, -α3.7/–SEA and -α4.2/–SEA were common and constituent ratios were 77.05%, 11.95%, 4.01%,3.65% and 2.10%, respectively, and altogether was 98.76%. Over all 7 934 cases, there were 1 691 cases with β-globin gene mutation over 13 kinds genotypes, and the incidence of β-thal was 21.31%, The mutation of CD41–42, IVS-II -654, CD17 and −28 were common, and constituent ratios were 34.24%, 29.80%, 16.03% and 10.70%, respectively, and altogether was 90.77%. Number of patients with screening test positive was the largest, and the incidence of the group with three indications was the highest. The abnormal percentage in group both with anemia symptom and screening test positive was the highest.ConclusionThere was a high thalassemia carrier rate among patients with clinical indications in our study. The main indication for diagnosis of thalassemia was both with anemia symptoms and screening test positive. The characteristics of thalamessia genotype in our study were consistent with that in southern China. It was important for population, especially reproductive population of high frequency area region to screening and diagnosing thalassemia.