Elevated hemoglobin A2 as a marker for β-thalassemia trait in pregnant women.
ABSTRACT β-thalassemia is one of the most prevalent inherited hemoglobin disorders. Compound heterozygotes or homozygous mutations of the β-globin chain gene account for severe cases of β-thalassemia that require lifelong transfusion, and make it necessary to identify β-thalassemia carries for prenatal diagnosis. The increase in hemoglobin A2 (HbA2) level is the most significant parameter in the identification of β-thalassemia carriers. HbA2, composing of two α chains and two δ chains, is a minor component of the hemoglobin present in normal adult red blood cells, accounting for about 2.5% of the total hemoglobin in healthy individuals. However, HbA2 level is also elevated in some pregnant women. This study aimed to evaluate the value of HbA2 level in the screening of pregnant women with β-thalassemia trait. Pregnant and non-pregnant women were randomly recruited who attended the prenatal care or diagnosis at our hospital located in Guangdong, a province in South China. Hemoglobin capillary electrophoresis was performed on high performance liquid chromatography to measure HbA2 levels in blood. The β-globin gene mutations were detected by the PCR-reverse dot-blot assay, and some were verified by direct sequencing. Pregnant women (n = 96) and non-pregnant women (n = 114) with normal HbA2 level (< 3.5%) had no β-thalassemia mutation. In contrast, pregnant women (n = 55) and non-pregnant women (n = 85) with elevated HbA2 level (≥ 3.5%) are β-thalassemia carriers. In conclusion, HbA2 level is a good marker for screening β-thalassemia trait in pregnant women in South China population.
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ABSTRACT: The analysis of DNA for the presence of particular mutations or polymorphisms can be readily accomplished by differential hybridization with sequence-specific oligonucleotide probes. The in vitro DNA amplification technique, the polymerase chain reaction (PCR), has facilitated the use of these probes by greatly increasing the number of copies of target DNA in the sample prior to hybridization. In a conventional assay with immobilized PCR product and labeled oligonucleotide probes, each probe requires a separate hybridization. Here we describe a method by which one can simultaneously screen a sample for all known allelic variants at an amplified locus. In this format, the oligonucleotides are given homopolymer tails with terminal deoxyribonucleotidyltransferase, spotted onto a nylon membrane, and covalently bound by UV irradiation. Due to their long length, the tails are preferentially bound to the nylon, leaving the oligonucleotide probe free to hybridize. The target segment of the DNA sample to be tested is PCR-amplified with biotinylated primers and then hybridized to the membrane containing the immobilized oligonucleotides under stringent conditions. Hybridization is detected nonradioactively by binding of streptavidin-horseradish peroxidase to the biotinylated DNA, followed by a simple colorimetric reaction. This technique has been applied to HLA-DQA genotyping (six types) and to the detection of Mediterranean beta-thalassemia mutations (nine alleles).Proceedings of the National Academy of Sciences 09/1989; 86(16):6230-4. · 9.74 Impact Factor