Noninvasive Prenatal Diagnosis for Cystic Fibrosis: Implementation, Uptake, Outcome, and Implications

Background: Noninvasive prenatal diagnosis (NIPD) for monogenic disorders has a high uptake by families. Since 2013, our accredited public health service laboratory has offered NIPD for monogenic disorders, predominantly for de novo or paternally dominantly inherited mutations. Here we describe the extension of this service to include definitive NIPD for a recessive condition, cystic fibrosis (CF).

Methods: Definitive NIPD for CF was developed using next-generation sequencing. Validation was performed on 13 cases from 10 families before implementation. All cases referred for CF NIPD were reviewed to determine turnaround times, genotyping results, and pregnancy outcomes.

Results: Of 38 referrals, 36 received a result with a mean turnaround of 5.75 days (range, 3-11 days). Nine cases were initially inconclusive, with 3 reported unaffected because the low-risk paternal allele was inherited and 4 cases in which the high-risk paternal allele was inherited, receiving conclusive results following repeat testing. One case was inconclusive owing to a paternal recombination around the mutation site, and one case was uninformative because of no heterozygosity. Before 2016, 3 invasive referrals for CF were received annually compared with 38 for NIPD in the 24 months since offering a definitive NIPD service.

Conclusions: Timely and accurate NIPD for definitive prenatal diagnosis of CF is possible in a public health service laboratory. The method detects recombinations, and the service is well-received as evidenced by the significant increase in referrals. The bioinformatic approach is gene agnostic and will be used to expand the range of conditions tested for.