Evaluation of beta-thalassemia in the fetus through cffDNA with multiple polymorphisms as a haplotype in the beta-globin gene.

Abstract

Invasive biopsy during the pregnancy is associated with an abortion risk of approximately 1% for the fetus. Free fetal DNA in maternal plasma is an excellent source of genetic material for prenatal molecular diagnoses. This study was conducted to investigate beta-thalassemia mutation in the fetus through maternal blood with multiple polymorphisms as haplotypes in the beta-globin gene. In this study, a total of 33 beta-thalassemia carrier (minor) couples were genotyped by ARMS-PCR for IVSII-IG>A mutation. During pregnancy, 10mL of blood was collected from pregnant women, and DNA was extracted by the magnetic bead-based extraction, and fetal DNA was enriched with AMPure XP kit. Five polymorphisms in 4 haplotype groups were evaluated by the Sanger Sequencing method. Finally, results were compared with those of the invasion method. Participants in study were 33 couples, mean age of the men was 26±5 years, and mean age of women was 23±4 years, and mean MCV, MCH, HbA2 blood parameters were 62.4±5.3, 19.6±3.1, 4.2±2.1 respectively. A total of 33 fetuses were genotyped for IVSII-IG>A mutation. Nine fetuses were affected, 10 fetuses were normal and 14 fetuses were carrier of beta-thalassemia. Sensitivity and specificity of Sanger Sequencing were equal to 88.8% and 91.6% respectively. Positive and negative predictive values were obtained as 80% and 95.6%, respectively. Mutational status of the fetus can be assessed by determining inheritance of paternally-derived alleles based on detection of haplotype-associated SNP in maternal plasma. Magnetic-based DNA extraction and fetal DNA enrichment are very simple and easy to perform and have satisfactory accuracy.