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Active cascade testing for carriers of cystic fibrosis gene
M Super1, M J Schwarz, G Malone
1Regional Genetics Service, Royal Manchester Children's Hospital, Pendlebury.
Insights
Cascade screening for cystic fibrosis carriers is highly effective and accepted by families. This method efficiently identifies carrier couples, enabling informed reproductive decisions and is recommended for broader application.
Area of Science:
- Medical Genetics
- Public Health
- Genetic Screening
Background:
- Cystic fibrosis (CF) is a genetic disorder requiring carrier identification.
- Extended family screening (cascade screening) is a potential strategy for CF carrier detection.
Purpose of the Study:
- To evaluate the acceptability, practicability, efficiency, and application of cascade screening for cystic fibrosis gene carriers.
- To assess the utility of cascade screening in identifying carrier couples within extended families of CF patients.
Main Methods:
- Cascade screening involved genotyping affected individuals and offering genetic testing to relatives and partners.
- Genetic counseling was provided via letter and formal sessions, with arrangements for prenatal diagnosis.
- Data collected included carrier couple detection rates, pregnancy outcomes, and screening uptake.
Main Results:
- 15 carrier couples were identified among 1563 tested relatives and partners.
- Eight of nine pregnancies in detected carrier couples underwent prenatal testing, with three terminations.
- An average of 16 family members per affected individual participated in screening.
Conclusions:
- Cascade screening for cystic fibrosis carriers is well-accepted, particularly by maternal relatives.
- This approach is significantly more efficient (10x) than unfocused screening for detecting carrier couples.
- The findings support the recommendation for widespread application of active cascade screening for CF carriers and suggest applicability to other recessive disorders.
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.