Screening for carriers of cystic fibrosis through primary health care services.

OBJECTIVE--To evaluate the uptake of cystic fibrosis carrier testing offered through primary health care services. DESIGN--Carrier testing for cystic fibrosis was offered to patients of reproductive age through primary health care services. SETTING--Three general practice surgeries and four family planning clinics in South West Hertfordshire District Health Authority. SUBJECTS--Over 1000 patients aged 16-44 attending two general practices and four family planning clinics and a stratified random sample of patients aged 16-44 from one general practice''s age-sex register. RESULTS--When screening was offered opportunistically the uptake was 66% in general practice and 87% in family planning clinics. Ten per cent of those offered a screening appointment by letter took up the invitation. Of the screened population, 76% had previously heard of cystic fibrosis, 35% realised it is inherited, and 18% realised that carriers need not have any family history. If they found themselves in an "at risk" partnership 39% would consider not having children and 26% would consider terminating an affected pregnancy, but in each case most people were unsure how they would react. CONCLUSIONS--Most people offered a cystic fibrosis test opportunistically wish to be tested, and the responses of those tested indicate that knowledge of carrier state would be considered in future reproductive decisions.     

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.     

Prenatal screening for cystic fibrosis carriers: an economic evaluation.

The cloning of the CFTR gene has made it technically possible to avert the unwanted birth of a child with cystic fibrosis (CF). Several large trials offering prenatal CF carrier screening suggest that such screening is practical and that identified carriers generally use the information obtained. Therefore, a critical question is whether the cost of such screening is justified. Decision analysis was performed that used information about choices that pregnant women were observed to make at each stage in the Rochester prenatal carrier-screening trial. The cost of screening per CF birth voluntarily averted was estimated to be $1,320,000-$1,400,000. However, the lifetime medical cost of the care of a CF child in today's dollars was estimated to be slightly>$1,000,000. Therefore, despite both the high cost of carrier testing and the relative infrequency of CF conceptions in the general population, the averted medical-care cost resulting from choices freely made are estimated to offset approximately 74%-78% of the costs of a screening program. At present, if it is assumed that a pregnancy terminated because of CF is replaced, the marginal cost for prenatal CF carrier screening is estimated to be $8,290 per quality-adjusted life-year. This value compares favorably with that of many accepted medical services. The cost of prenatal CF carrier screening could fall to equal the averted costs of CF patient care if the cost of carrier testing were to fall to $100.     

Quinquennial cervical smears: every woman's right and every general practitioner's responsibility.

Out of 558 women aged 16 to 64 who were registered with one general practitioner, 459 were eligible to be screened for cervical cancer. Even though the practice had been taking cervical smears for many years, they were predominantly from women under 35. Of the eligible women between 35 and 64, 111 (37%) had never had a smear. After short term intensive screening the uptake rates, defined by a smear done within the past five years, rose to 100% for women under 35, 94% for those aged 35 to 64, and 96% for all eligible women. Screening was rewarding both in its clinical yield and in the income generated by item of service payment. The success of screening was largely due to the participation of practice nurses in taking smears, and to a new method of recording smear results and claims for them. Some women, however, refused to have cervical smears.     

Screening for asymptomatic bowel cancer in general practice.

General practitioners screened 4284 asymptomatic people aged over 40 to compare the incidence of large bowel cancer and polyps with a control general practice (4288 patients). Compliance was best in young women (60%), and overall it was 42%. Twenty six patients who had a positive Haemoccult test result (1.5% of those screened) were examined by colonoscopy and 10 had polyps. The incidence of cancers in the two groups was similar but in the control (unscreened patients) practice no polyps were found.     

A test of the heterozygote-advantage hypothesis in cystic fibrosis carriers.

We report a test of the hypothesis that the high frequency of cystic fibrosis (CF) in Caucasian populations is due to a fertility advantage in CF carriers. One hundred forty-three grandparent couples of Utah CF cases were compared with 20 replicate sets of matched control couples drawn from the Utah Genealogical Database. Ascertainment correction, which has not been applied in previous studies of CF carrier fertility, was applied to these data. Before ascertainment correction was applied, CF carriers appeared to manifest a significant fertility advantage over controls. After the correction formula was applied, this difference disappeared. Carriers and controls were also compared in terms of the length of intervals between births. Again, no significant differences were found. It was concluded that fertility differences are unlikely to account for the observed Caucasian CF gene frequency. Other mechanisms, particularly a past selective event or random genetic drift, are more likely to be responsible.     

Antenatal screening for carriers of cystic fibrosis: randomised trial of stepwise v couple screening.

OBJECTIVE--To perform a rigorous comparative evaluation of stepwise and couple approaches to antenatal carrier screening for cystic fibrosis. DESIGN--Pragmatic randomised trial. SETTING--Hospital antenatal clinic serving a regional population. SUBJECTS--2002 women (couples) attending for booking antenatal visit at less than 17 weeks'' gestation with no family history of cystic fibrosis. INTERVENTIONS--Offering counselling and carrier testing for cystic fibrosis, either to women in the first instance (stepwise) or to couples (couple screening). MAIN OUTCOME MEASURES--Uptake rates; anxiety; knowledge of cystic fibrosis and carrier status (both partners); attitudes to health, pregnancy, the baby, and screening (both partners); and uptake of carrier testing by relatives. RESULTS--Uptake of screening was the same for both approaches (90%). After delivery most women remembered test results and their meaning, but 53/253 (21%) of those with negative results of couple testing had forgotten that repeat testing would be advisable if they had a pregnancy with a new partner. With stepwise screening women identified as carriers had high levels of anxiety when results were received (mean anxiety score 52.3). This dissipated with a reassuring partner''s result (carriers'' mean anxiety score 36.1) to levels similar to those receiving negative results from couple screening. Of those receiving negative results, women who had stepwise screening were significantly less anxious than those who had couple screening (mean score with result 32.1 v 35.4, 95% confidence interval for difference -4.7 to -2.1). CONCLUSIONS--Couple screening allows carriers to avoid transient high levels of anxiety, but is associated with more anxiety and false reassurance among most screenees who will test negative. Stepwise screening gives carriers and their relatives genetic information and is, in our opinion, the better method.