J Med Assoc Thai 2010; 93 (11):1243

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Analysis of Real-Time PCR Cycle Threshold of α-Thalassemia-1 Southeast Asian Type Deletion Using Fetal Cell-Free DNA in Maternal Plasma for Noninvasive Prenatal Diagnosis of Bart’s Hydrops Fetalis
Pornprasert S Mail, Sukunthamala K , Kunyanone N , Sittiprasert S , Thungkham K , Junorse S , Pongsawatkul K , Pattanaporn W , Jitwong C , Sanguansermsri T

Background: Noninvasive prenatal diagnosis based on detection of fetal cell-free DNA is hampered when mother and father
are both carriers for the same autosomal recessive mutation.

Objective: To compare the diagnosis of Bart’s hydrops fetalis using conventional Gap-PCR analysis of fetal cells/tissues
with the measurement of quantitative difference (ΔCT) between α-thalassemia-1 SEA type deletion gene (CT-mutant) and wild
type α-globin gene (CT-wild type) in plasma of pregnancies by using the Taqman real-time quantitative PCR.

Material and Method: Plasma DNA samples were collected from three groups of pregnancies whose fetuses have known
thalasemia status (7 normal, 11 heterozygote α-thalassemia-1 SEA type deletion, and 7 Bart’s hydrops fetalis). The
α-thalassemia-1 SEA type deletion gene and wild type α-globin gene were quantified by using Taqman real-time quantitative
PCR and then the ΔCT was analyzed by subtracting the CT-mutant from CT-wild type.

Results: Mean ΔCT values were not significantly different among the three groups. However, women whose fetuses were
diagnosed as Bart’s hydrops fetalis had a higher proportion (43%) of plasma DNA samples that had negative ΔCT value
than women whose fetuses were diagnosed as normal or heterozygote α-thalassemia-1 SEA type deletion (0 and 27%, respectively).

Conclusion: Further investigations are needed to improve the diagnosis of Bart’s hydrops fetalis using fetal cell-free DNA.

Keywords: α-thalassemia-1 SEA type deletion, Bart’s hydrops fetalis, Fetal cell-free DNA, Prenatal diagnosis, Real-time PCR

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