Screening results and analysis on genotype of thalassemia in 108 140 anemia patients in Chongqing

Abstract

Objective To investigate the genotypes and distribution characteristics of thalassemia in Chongqing. Methods A total of 108 140 peripheral blood samples were harvested from 36 districts and counties in Chongqing during January 2018 and November 2019. Single-tube multiplex polymerase chain reaction (PCR) and reverse spot-strip hybridization (RDB) were employed to detect 3 common α-thalassemia genotypes and 17 common β-thalassemia point mutations. The results were analyzed statistically. Results A total of 9 988 (9.24%) thalassemia carriers were identified, and among them, 5 448 were carriers of α-thalassemia gene mutation, with a detection rate of 5.04% (5 448/108 140), with --SEA/αα deletion genotype most common (accounting for 45.71% of α-thalassemia). Detection of 13 genotypes of β-thalassemia detected 4 368 patients with β-thalassemia gene mutations, with a detection rate of 4.04% (4 368/108 140), and 4 359 patients of them (99.8%) were heterozygous, mainly CD41-42 (-CTTT), CD17 (AAG>TAG) and IVS2-654(C>T). One homozygous case was firstly reported in Chongqing, and the left 8 cases (0.18%) were double heterozygous. Two types of double heterozygous mutations, CAP (A-C)/IVS2-654 (C>T) and CD17 (AAG>TAG)/βE (GAG>AAG) were not reported in China. For the 172 patients who were confirmed as composite α- and β-thalassemia carriers, the detection rate was 0.16%, and the most common genotype was -α3.7/αα with CD41-42(-CTTT). The incidence of composite α- and β-thalassemia in this study was at the middle level in China. There were totally 4 triple heterozygous mutants among the composite thalassemia, and triple heterozygous mutations of (-α4.2/αα, βE(GAG>AAG), IVS2-654(C>T), -α3.7/αα, -α4.2/αα, -29(A-G) and -α3.7/αα, -α4.2/αα, CD17(AAG>TAG)) were not reported yet in our country. Conclusion Regional characteristics is found in the gene mutation composition ratio of thalassemia in Chongqing region. The incidences of α-thalassaemia and β-thalassaemia are lower than those of Guangdong and Guangxi regions, and the incidence of composite α- and β-thalassemia is in the middle level of our country. Five mutant genotypes are identified for the first time in China.

Keywords

• thalassemia
• genotype
• chongqing