β-地中海贫血复合缺失型α-地中海贫血双重杂合子的分子检测及血液学分析

本研究对β-地中海贫血复合缺失型α-地中海贫血双重杂合子进行分子检测及血液学表型分析，以了解其检出情况及基因分布状况。采用单管多重gap—PCR技术检测3种常见的缺失型α-地中海贫血基因；采用PCR结合反向点杂交法检测β-珠蛋白基因17个位点的18种突变；进行血细胞常规分析。结果表明：81例β-地中海贫血杂合子中有15例复合缺失型α-地中海贫血，占18．52％。共有9种基因型，包括6例（7．41％）β-地中海贫血杂合子携带α-地中海贫血-1基因（--^SEA／αα-）；8例（9．88％）携带α-地中海贫血-2基因，其中6例（7．41％）为右侧缺失型（-α^3.7／αα），2例（2．47％）为左侧缺失型（-α^4.2／αα）；1例（1．23％）携带缺失型HbH基因（--^SEA／-α^3.7）。β-地中海贫血复合缺失型α-地中海贫血双重杂合子的各项红细胞参数与单纯β-地中海贫血杂合子比较差异无显著性意义（P〉0．05）。结论：梧州市β-地中海贫血复合缺失型α-地中海贫血双重杂合子的发生率很高，而血液学指标缺乏特异性。采用gap—PCR作为临床上地中海贫血筛查的一线方法，可以有效减少β-地中海贫血复合α-地中海贫血双重杂合子漏检的可能，对遗传咨询和准确进行产前诊断具有重要意义。

Molecular Detection and Haematological Analysis of Heterozygotes in β-Thalassemia Combining Deletional α-thalassemia

This study was aimed to investigate the prevalence and genotype distribution of heterozygotes in beta-thalassemia combining deletional alpha-thalassemia by using molecular detection and haematological methods. Three common deletions of alpha-thalassemia were detected by using gap-PCR. The mutations of beta-thalassemia were identified by using PCR with reverse dot blot hybridization. The routine analysis of blood cells was carried out. The results indicated that 15 cases from the 81 beta-thalassemia traits were found to be the compound heterozygosity for beta-thalassemia and alpha-thalassemia with 9 different types of gene defects with 18.52% detection rate. There were 6 cases (7.41%) of beta-thalassemia heterozygote combining alpha-thalassemia-1 gene (--(SEA)/alphaalpha), 8 cases (9.88%) combining with alpha-thalassemia-2 gene including 6 (7.41%) right ward deletion (-alpha(3.7)/alphaalpha) and 2 (2.47%) left ward deletion (-alpha(4.2)/alphaalpha), and 1 case (1.23%) combining deletional HbH gene (--(SEA)/-alpha(3.7)). No significant differences were found between beta-thalassemia heterozygotes combining deletional alpha-thalassemia and pure beta-thalassemia in all RBC parameters. It is concluded that the incidence of beta-thalassemia heterozygotes combining with deletional alpha-thalassemia is frequent in Wuzhou city. The hematological analysis can not give specificity for diagnosing these dual heterozygotes. Gap-PCR as a routine method for thalassemia screening has the advantages in reducing the possibility of failing to detect the combining heterozygosity for beta-thalassemia and alpha-thalassemia. It is more useful for genetic counselling and prenatal diagnosis of this disease.