Cascade carrier-testing in cystic fibrosis.

It is good medical practice to offer carrier tests and counselling to the relatives of those affected by recessive disorders. Many are concerned about their own chances of having affected offspring. Cystic fibrosis carrier tests have been feasible since the discovery of the gene in 1989. It was generally agreed that although population screening was not practical, testing should be offered to relatives and their partners. There is evidence that such offers have not always been made and relatives have sometimes found it difficult to be tested. An active cascade programme of the counselling and testing of cystic fibrosis patients' relatives and their partners has operated from Royal Manchester Children's Hospital since 1993. The service operates with dedicated staff, backed up by a specialist cystic fibrosis molecular genetics laboratory and a specialist genetic counselling service. The main target groups are couples or individuals of child-bearing age. There is discouragement of the testing of young children and of grandparents beyond reproductive age, although, if parents or individuals are insistent, testing is often performed, after counselling. An audit of users has shown satisfaction, very few feeling that they were pressured into having the tests. The experience of other centres with cascade-testing in cystic fibrosis is summarised. Cascades can start whenever a sufferer or carrier is identified, although care should be exercised in instituting active cascades in the extended families of newborns identified as carriers in neonatal screening programmes.