RESUMO
OBJECTIVE: To assess the diagnostic performance of a novel circulating single molecule amplification and re-sequencing technology (cSMART) method for noninvasive prenatal testing (NIPT) of Phenylketonuria (PKU). DESIGN: Blinded NIPT analysis of pregnancies at high risk for PKU. SETTING: Shanghai Xinhua Hospital and Hunan Jiahui Genetics Hospital, China. POPULATION: Couples (n = 33) with a child diagnosed with PKU. METHODS: Trio testing for pathogenic PAH mutations was performed by Sanger sequencing. In second pregnancies, invasive prenatal diagnosis (IPD) was used to determine fetal genotypes. NIPT was performed using a PAH gene-specific cSMART assay. Based on the plasma DNA mutation ratio relative to the fetal DNA fraction, fetal genotypes were assigned using a maximum-likelihood algorithm. MAIN OUTCOME MEASURES: Concordance of fetal genotyping results between IPD and NIPT, and the sensitivity and specificity of the NIPT assay. RESULTS: Compared with gold standard IPD results, 32 of 33 fetuses (96.97%) were accurately genotyped by NIPT. The sensitivity and specificity of the NIPT assay was 100.00% (95% CI 59.04-100.00%) and 96.15% (95% CI 80.36-99.90%), respectively. CONCLUSIONS: The novel cSMART assay demonstrated high accuracy for correctly calling fetal genotypes. We propose that this test has useful clinical utility for the rapid screening of high-risk and low-risk pregnancies with a known history of PKU on one or both sides of the family. TWEETABLE ABSTRACT: NIPT of couples at high risk for PKU using a full-coverage cSMART PAH gene test.
