Discrepant Results on Two Different Single Gene Non-invasive Prenatal Tests for Cystic Fibrosis: A Case Report.

Background Prenatal cell-free DNA (cfDNA) screening has revolutionized the prenatal detection of fetal aneuploidy and other conditions. Originally designed to identify risk for trisomy 21, cfDNA screening has expanded to other fetal aneuploidies, microdeletion syndromes, dominant de novo single-gene disorders, and now autosomal-recessive single-gene conditions. The advancement of cfDNA screening offers patients and providers more options for prenatal risk assessment. Case A 34-year-old G2P1001 patient received a false-negative result from one single-gene noninvasive prenatal testing (sgNIPT), also known as prenatal single-gene cfDNA screening, for fetal cystic fibrosis, followed by a discrepant true-positive result on a different sgNIPT platform. The patient has a prior child affected with cystic fibrosis. The second laboratory returned a high-risk result for fetal cystic fibrosis, which was confirmed with diagnostic amniocentesis. Conclusion Prenatal sgNIPT screening should be individualized after appropriate counseling on the benefits and limitations of available screening and diagnostic tests. While diagnostic amniocentesis remains the society-recommended gold standard for prenatal diagnosis of autosomal-recessive conditions, these new, noninvasive technologies provide more options for patients who either do not want to assume the risks associated with or to better guide decision-making for diagnostic testing.