Detection of paternal alleles in maternal plasma for non-invasive prenatal diagnosis of β-thalassemia: A feasibility study in southern Chinese

ObjectiveTo evaluate in maternal plasma, the efficacy of detecting the paternal β-gene mutation and informative single nucleotide polymorphisms (SNPs) linked to the paternal-mutant or -normal allele in non-invasive prenatal diagnosis (NIPND).Study designIn 20 at-risk pregnancies, using the allele-specific arrayed primer extension (AS-APEX) technology of the previously published “Thalassemia” array, cyanine-5-deoxycytosine triphosphate (Cy5-dCTP) was incorporated into the extended strands to matched PCR-amplified maternal plasma DNA templates, to detect both the paternal β-gene mutation and informative paternal SNPs.ResultsSensitivity experiment showed that 5 pg DNA as starting template gave detectable signals on the array. In 13 cases (65%), the paternal-derived β-gene mutation and/or informative mutant-associated SNP were detected. A subsequent invasive procedure was required to determine if the fetus had a β-thalassemia (thal) major or minor genotype. In 3 cases (15%), absence of the paternal mutant or mutant-associated SNP excluded a β-thal major fetus; while in 4 cases (20%), this approach was non-discriminative as both parents carry the same mutation without any informative SNP.ConclusionThis approach was useful in 16 out of 20 (80%) pregnancies at risk for β-thal in southern Chinese.