We propose using a modified amplification refractory mutation system real-time polymerase chain reaction (ARMS RTPCR) technique to exclude the invasive prenatal diagnosis for a non-paternally inherited beta thalassemia mutation in couples atrisk for having a baby with CHBT. The ARMS RT-PCR method was performed for 36 at-risk couples by using isolated fetal cell-free DNA from maternal plasma. The modified ARMS RT-PCR primers targeted one of the following paternally inherited beta thalassemia mutation: -28 A→G, CD17 A→T, CD 26 G→A, IVS1-1 G→T and CD 41-42 -CTTT. The method could be successfully employed for NIPST starting with the 7th week of gestation. The results showed that 19 pregnant women were negative for PIBTM (53%). After an on-track and on-time of one year, including postnatal thalassemia blood tests, none of the babies showed symptoms or signs of beta thalassemia disease. We concluded that the modified ARMS RT-PCR method was an accurate, cost-effective and feasible method for use as a NIPST for at-risk couples with the potential of having a baby with CHBT.
We assessed whether urinary DNA sediment was a feasible sample type for the molecular diagnosis of α-thalassemia (α-thal) mutations. Urine samples (5-10 mL) were collected from 218 male and female volunteers. The cells were centrifuged, and DNA was isolated according to the protocol of a commercial DNA isolation kit. Detection of the α(0)-thal [Southeast Asian (- -(SEA)) and - -(THAI)] deletions was performed using quantitative real-time polymerase chain reaction (q-PCR), in addition to conventional gap-PCR. The results revealed that DNA extracted from urinary sediment presented an average DNA content of 11.2 ± 5.5 ng/µL, and the 260/280 ratio indicative of DNA purity, was 1.2 ± 0.2. The overall q-PCR threshold cycle was 31.2 ± 2.3. The melting temperature for the - -(SEA) deletion was 87.3 ± 0.1 °C, while that of the wild type sequence was 92.5 ± 0.2 °C. There were 16 (7.3%) α(0)-thal SEA genotypes detected. These results were in agreement with those of the conventional gap-PCR and blood DNA analyses. Thus, DNA from urinary sediment can be efficiently used for the molecular diagnosis of α(0)-thal mutations. This approach allows for rapid diagnosis, is non invasive, and could be useful for preventing Hb Bart's (γ4) hydrops fetalis syndrome.
We propose antenatal blood tests using high-resolution DNA melting (HRM) analysis for beta thalassemia mutation detection after hemoglobin A2 estimation as a modified strategy for the identification of beta thalassemia at-risk couples. Antenatal blood samples of 1,115 couples were transferred from the antenatal care clinic. Hemoglobin A2 was quantified, and proportions ≥3.5% were further assessed for beta thalassemia mutation using HRM analysis. Twelve types of beta thalassemia mutations, including hemoglobin E, were identified. There were 23 couples who were detected as at-risk. All at-risk couples were identified within 7 working days after sample receipt. Prenatal diagnosis revealed 6 affected fetuses. One fetus was homozygous CD17 (AT), and five fetuses exhibited beta0 – thalassemia/hemoglobin E disease. These results were consistent with the outcomes calculated using the Hardy-Weinberg equation. Antenatal blood tests for mutation detection using high-resolution DNA melting analysis after hemoglobin A2 estimation is a feasible laboratory method for the recruitment of couples with a fetus that is at risk for beta thalassemia. This modified strategy is cost-effective and may be beneficial for use in a beta thalassemia prevention program.
We propose a fast-track strategy [direct blood DNA analysis using a quantitative real-time polymerase chain reaction (PCR) technique] for the early risk detection and prenatal diagnosis of a(0)-thalassemia (SEA and Thai deletion). Blood DNA samples were obtained from a volunteer group of 1235 ANC couples. They were assessed using quantitative real-time PCR to detect carriers of a(0)-thalassemia (SEA and Thai deletion). At-risk couples were identified, and further prenatal diagnosis by amniocentesis was implemented. Fetal DNA was isolated from the amniotic cells and characterized by quantitative real-time PCR to detect the a(0)-thalassemia mutation, which was reconfirmed using the droplet digital PCR method. Fifteen at-risk couples were identified. The timing of prenatal diagnosis was appropriate for all couples and four of the fetuses were diagnosed with Bart's hydrops fetalis. The results were compatible with those calculated using the Hardy-Weinberg equation for a recessively inherited single gene disorder. The conclusion was that the fast-track strategy could shorten screening policy timelines, promoting early risk detection for couples and early prenatal diagnosis. The fast-track strategy might be beneficial for the prevention of hemoglobin Bart's hydrops fetalis syndrome.
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