Analyzing maternal plasma with droplet digital PCR (ddPCR) may be accurate and effective for noninvasive prenatal diagnosis (NIPD) of Southeast Asian (SEA) deletion alpha-thalassemia, according to research published in Biomedical Reports.

The SEA deletion is the most common cause of alpha-thalassemia in the Asian population and can be passed down, causing Hb Bart’s hydrops fetalis. Thailand has a high prevalence of beta-thalassemia, which can cause anemia and other complications in children born with the condition.

Prenatal screening for thalassemia has gained prominence in Asia. NIPD with cell-free fetal DNA detects disease-causing mutations in the fetus. The current study developed ddPCR-based assays to detect fetal alpha- and beta-thalassemia on 46 pregnant women who are carriers of thalassemia mutations. A total of 22 had SEA deletion, 16 had an HbE (G>A) mutation, and 8 had a 41/42 (-CTTT) mutation.

The study used ddPCR to assess the copy number of SEA deletion in unprocessed cell-free DNA from maternal plasma. The SEA assay was able to detect Hb Bart’s hydrops fetalis with 95% sensitivity and 91% specificity.


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The assay for HbE and 41/42 (-CTTT) mutations did not meet the requirements for clinical use, but the authors noted that the HbE results were promising. A total of 10 of 16 samples were classified correctly, 3 were inconclusive and may be correctly classified with additional ddPCR, and 3 were misclassified. Of the 8 samples for 41/42 (-CTTT) mutations, 4 were inconclusive and 2 were correctly classified.

DdPCR-based assays can be reliably detected for SEA deletion alpha-thalassemia, but the technique cannot be recommended for HbE and 41/42 (-CTTT) mutations. The results are limited by a low sample size of these mutations.

Reference

Sawakwongpra K, Tangmansakulchai K, Ngonsawan W, et al. Droplet-based digital PCR for non-invasive prenatal genetic diagnosis of α and β-thalassemia. Biomed Rep. 2021;15(4):82. doi:10.3892/br.2021.1458

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