Cascade testing in families of carriers identified through newborn screening in Western Brittany (France)

Highlighting the impact of cascade carrier testing in cystic fibrosis families

BACKGROUND

Cascade carrier testing within cystic fibrosis (CF) affected families offers relatives of CF patients the opportunity to know their status regarding the mutation that segregates within their family, and thus to make informed reproductive choices. As an Australian study has recently shown that this test seemed underused, we searched to assess uptake of this test in a European area where CF is common, and to report its public health implications.

METHODS

This study relied on 40 CF-affected families from western Brittany, France. Investigations included drawing of family trees and registration of carrier tests performed in those families.

RESULTS

Of the 459 relatives eligible for testing, 185 were tested, leading to an adjusted uptake rate of testing of 40.7% (95% CI: [34.1%; 47.3%]). The main predictors for having testing were being female (p=0.031) and having a high prior risk (p<0.001). Planning a pregnancy or expecting a child (reported in at least 38.4% of tested relatives) also appeared critical in choosing to be tested. Overall, carrier testing allowed to reassure more than 1/4 of the relatives and to detect five new 1-in-4 at-risk couples who then requested prenatal diagnosis.

CONCLUSIONS

This observational study assesses, for first time in Europe, uptake of CF cascade carrier testing within CF families, which is a critical tool to reassure non-carriers and to detect early new at-risk couples.