Active cascade testing for carriers of cystic fibrosis gene.

OBJECTIVE

To examine the acceptability, practicability, efficiency, and application of active screening for carriers of the cystic fibrosis gene in the extended families of those in whom the disease is present (Cascade screening).

DESIGN

Paediatricians and physicians provide details of their affected patients, pedigrees are drawn up, and relatives offered tests after initial contact by the affected nuclear families. Affected patients are genotyped in a laboratory with a special interest in the genetics of cystic fibrosis.

SETTING

North Western health region.

SUBJECTS

Relatives and partners of 607 people with cystic fibrosis.

INTERVENTIONS

Genetic counselling by letter for people found to be carriers; formal genetic counselling and when indicated arrangements for prenatal diagnosis for couples discovered to be carriers.

MAIN OUTCOME MEASURES

Number of carrier couples detected; action in pregnancy of detected carrier couples; extent of the uptake of screening by relatives.

RESULTS

Of 1563 relatives or partners tested, 15 carrier couples were detected; of nine pregnancies undertaken by these 15, eight had prenatal tests and three terminated pregnancies. An average of 16 people per family have come forward for testing so far.

CONCLUSIONS

Cascade screening for carriers of cystic fibrosis is well accepted by relatives, especially on the mother's side of the family; it is 10 times more efficient in detecting carrier couples than unfocused screening. Detected carrier couples make practical use of the information in pregnancy. Active cascade screening for carriers is effective in cystic fibrosis and widespread application is recommended. These principles could be applied to other recessive disorders.