Cascade testing for carrier status in cystic fibrosis in a large family

The offer to determine carrier status for cystic fibrosis (CF) was made to the 230 descendants of a couple who were presumed to carry the delta F508 mutation. "Cascade testing" was employed, in which the mutation is followed from the oldest generation down. Compliance was over 75% and family members were relieved of the anxiety engendered by uncertainty. In one couple considering having a family, both partners were found to be carriers.