Antenatal screening for cystic fibrosis: a trial of the couple model

How does carrier status for recessive disorders influence reproductive decisions? A systematic review of the literature

Introduction: Carrier screening for recessive disorders is undertaken by prospective parents to inform their reproductive decisions. With the growing availability of affordable and comprehensive expanded carrier screening (ECS), it is expected that carrier screening will become a standard practice in the future. However, the impact of positive carrier screening results on the reproductive decisions of at-risk couples (ARCs) remains underexplored.Areas covered: We performed a systematic literature review to identify peer-reviewed publications describing the reproductive decisions of ARCs. Our search identified 19 relevant publications spanning the period 1994-2018. By synthesizing available evidence, we found that most ARCs chose to prevent the birth of an affected child and the decision to utilize preventive reproductive options was strongly influenced by the clinical nature of a disorder. However, there was also some heterogeneity in reproductive decisions within the same recessive disorders, suggesting that choices of ARCs can be influenced by factors other than the clinical nature of a disorder.Expert opinion: ECS is becoming increasingly common, which will result in the routine identification of many ARCs. Reproductive decision-making by ARCs is a complex and emotionally challenging process, highlighting the critical role of genetic counseling in the care for these potentially vulnerable patients.

Population-based carrier screening for cystic fibrosis: a systematic review of 23 years of research

Cystic fibrosis is the most common severe autosomal recessive disease, with a prevalence of 1 in 2,500-3,500 live births and a carrier frequency of 1 in 25 among Northern Europeans. Population-based carrier screening for cystic fibrosis has been possible since CFTR, the disease-causing gene, was identified in 1989. This review provides a systematic evaluation of the literature from the past 23 years on population-based carrier screening for cystic fibrosis, focusing on the following: uptake of testing; how to offer screening; attitudes, opinions, and knowledge; factors influencing decision making; and follow-up after screening. Recommendations are given for the implementation and evaluation of future carrier-screening programs.

Cystic fibrosis carrier screening

Carrier screening for cystic fibrosis (CF) has been available since the early 1990s, yet there are few programs, and none funded as part of a national health care strategy. The aim of this paper is to provide a description of carrier screening for CF and examine the progress that has been made towards the establishment of universal population-based carrier screening programs. This is an evidence based commentary on population-based carrier screening for CF. Peak body recommendations were examined and existing programs for CF carrier screening are reviewed. The attitudes from the non-CF community, CF healthcare professionals and people with CF were studied. Data from health economic assessments is examined. The future of carrier screening for CF in the context of advancing genetic technologies and potentially curative therapies is considered.

Possibilities and barriers in the implementation of a preconceptional screening programme for cystic fibrosis carriers: a focus group study

OBJECTIVE

This qualitative study aimed to explore possibilities and barriers in the implementation of a nationwide preconceptional cystic fibrosis (CF) carrier screening programme.

METHODS

Sessions were held with two focus groups of CF patients and CF relatives, one focus group of people from the target population (couples planning a pregnancy), and two focus groups of potential providers (general practitioners (GPs) and municipal health service workers).

RESULTS

Important barriers in the implementation of a preconceptional CF carrier screening programme included the problem of reaching the target population, the heavy workload of GPs, the limited public knowledge about CF in general, and the absence of a preconceptional consultation setting. In general, there was a positive attitude among the participants towards CF carrier screening.

CONCLUSION

This study revealed some important barriers in the implementation of CF carrier screening programmes. More research is needed to specify and quantify the importance of the various barriers. Eventually, different intervention strategies should be included in an implementation plan to overcome the most important barriers in the organization and execution of screening.

Population screening for cystic fibrosis: knowledge and emotional consequences 18 months later

We assessed cystic fibrosis (CF) knowledge and emotional consequences of CF population testing 18 months after screening was offered. Questionnaires were sent to 593 individuals and 353 responded (59.5%). All respondents had sound knowledge of CF disease, although carriers were more likely to correctly state the pattern of CF inheritance and CF carrier rate in Australia. Eleven of 47 carriers falsely believed they were only very likely to be carriers, while nearly a third of test-negative individuals falsely believed they were definitely not carriers. Imprecise recall of the meaning of results may be due to memory loss over time, simplification of result meaning and minimization of risk. The Health Orientation Scale (HOS) was used to assess emotional consequences of CF carrier testing 18 months after testing. Both carriers and test-negative individuals thought most carriers would experience more negative feelings than most non-carriers. Carriers experienced less positive feelings about their test result compared to non-carriers. Interestingly, the carriers' own feelings about their result were more positive compared to how they thought most carriers would feel. These results suggest that carriers experience minimal adverse psychological effects, although a negative social stigma may be attached to carrying the CF gene mutation.

Cystic fibrosis: selecting the prenatal screening strategy of choice

Cystic fibrosis is a serious disorder. Research into the treatment of affected individuals is in progress, but a cure is not expected in the near future. In this review, we demonstrate that prenatal screening for cystic fibrosis meets the requirements for a worthwhile screening programme. We explain the reasons that have led us to conclude that one approach ('couple screening') is the method of choice. The couple-based approach calls for reporting results to the couple as a unit. Only if both parents are found to be carriers is the result designated screen-positive and an amniocentesis or chorionic villus sampling offered. This offers a substantial reduction in the proportion of women with unaffected pregnancies with positive results (the false-positive rate) compared with other methods without reducing the detection of affected pregnancies. It also avoids creating a screen-positive group for which no definitive diagnosis is available. This is a problem with other screening methods. The couple method can achieve a 72% detection rate for a 0.1% false-positive rate. The screening method is simple, non-invasive, reliable, safe and reasonably cost effective. Existing programmes have shown that screening using this method is acceptable to health care professionals and patients. Setting up a national prenatal screening programme for cystic fibrosis is timely and should be implemented using the couple screening method.

Evaluation of cystic fibrosis carrier screening programs according to genetic screening criteria

Genetic screening programs should meet certain criteria before they can be introduced into the community. The aim of this study was to discuss pilot studies for cystic fibrosis (CF) carrier screening before and during pregnancy in the light of important genetic screening criteria. Overall, CF carrier screening meets the prerequisites that justify screening. However, more specific criteria for the development of screening programs were not always taken into consideration. Most project leaders concentrated on uptake as an important outcome, and less on informed decision-making. To further investigate the long-term psychological and social effects of genetic screening, continuous monitoring of screening projects is recommended.

Research directions in genetic counselling: a review of the literature

There is a growing body of literature considering genetic counselling services in a variety of clinical settings. This literature encompasses both predictive and diagnostic testing, from the viewpoints of service providers and recipients. It also embraces a wide range of conceptions of the nature and goals of genetic counselling. However, research in this area has been criticised for a focus on outcome rather than process, and it has been suggested that this focus limits its practical use. The purpose of this review is twofold: (1) to describe the varying concepts of counselling which appear to be utilised in published work and (2) to discuss the possible applications of this work to practice.

Population screening for cystic fibrosis in Western Australia: community response

We measured acceptance of carrier testing for cystic fibrosis in the community when offered in a primary care setting, determined variables influencing acceptance, and assessed knowledge of cystic fibrosis 3-6 months later. A total of 5,102 individuals age 18-50 years attending general practices or a family planning clinic in Western Australia completed questionnaires about knowledge of cystic fibrosis and the State Anxiety Inventory. Testing for the delta F508 gene was offered. After 3-6 months, carriers, a sample of consenting participants who were not tested, and a sample of test-negative participants were sent a further questionnaire; 43.5% of participants chose to be tested for cystic fibrosis carrier status. Women, younger people, people with higher education, people without children, and people planning to have children were more likely to be tested. After 3-6 months, carriers gave correct responses to questions about cystic fibrosis more frequently than those who tested negative or were not tested; 82.2% of carriers knew that they were definitely a carrier and 31.1% of test-negative individuals believed they were definitely not carriers. Thus, population carrier screening for cystic fibrosis offered in a community setting in Western Australia was acceptable to almost half of those offered testing, particularly younger people and those planning to have children, for whom knowledge of carrier status could be useful in making reproductive decisions. There was evidence that tested individuals recalled information in a way that minimised their risk of being a carrier.

Incorrect recall of residual risk three years after carrier screening for cystic fibrosis: a comparison of two-step and couple screening

OBJECTIVE

This study was undertaken to compare long-term recall of the meaning of test results after a negative result of 2-step or couple antenatal screening.

STUDY DESIGN

In a randomized controlled trial a subject-completed questionnaire was sent to 275 women who had undergone couple testing 3 years earlier and 83 women who had undergone 2-step testing 3 years earlier (n = 263/358 for a response rate of 73%). The main outcome measure was understanding of test results.

RESULTS

Three years after testing women who had undergone couple testing were 4.5 times (95% confidence interval 2.4-8.4 times) more likely than those who had undergone 2-step testing to accurately recall that the test result meant that they were unlikely to be carriers for cystic fibrosis (80%, 95% confidence interval 74%-86%, versus 49%, 95% confidence interval 36%-61%). Anxiety level, plans to have more children, and age were unrelated to recall.

CONCLUSION

The results of this study, together with those from other evaluations, suggest that not only does couple testing avoid the high levels of anxiety associated with 2-step testing but it also results in greater awareness of the residual risk inherent in a negative screening test result.

Issues in implementing prenatal screening for cystic fibrosis: results of a working conference

PURPOSE

To summarize a conference convened to examine how cystic fibrosis screening might appropriately be introduced into routine prenatal practice.

METHODS

Participants included experts from various relevant disciplines. Systematic reviews and data from individual trials were presented; issues were identified and discussed.

RESULTS

Judged by published criteria, prenatal cystic fibrosis screening is suitable for introduction. Screening can be performed cost-effectively by identifying racial/ethnic groups at sufficient risk and then using either of two models for delivering laboratory services. Validated educational materials exist. Ethical issues are not unique.

CONCLUSIONS

Once adequate facilities for patient and provider education, testing, counseling, quality control, and monitoring are in place, individual programs can begin prenatal screening for cystic fibrosis.

Cystic fibrosis screening: a fetus with hyperechogenic bowel may be the index case

BACKGROUND

The potential of hyperechogenic fetal bowel to act as a hallmark for prenatal cystic fibrosis screening in the general population is controversial.

METHODS

Our goal was to evaluate the incidence of cystic fibrosis in 209 fetuses with hyperechogenic bowel diagnosed at routine ultrasonography and with no family history of cystic fibrosis. The diagnosis of cystic fibrosis was based on prenatal screening for the eight mutations most frequently observed in France (deltaF508, deltaI507, 1717-1G-->A, G542X, G551D, R553X, W1282X, N1303K) and at postnatal follow up.

RESULTS

The overall incidence of cystic fibrosis was 7/209 (3.3%) which is 84 times the estimated risk of CF in the general population (112500). Of these seven cases, six were diagnosed prenatally based on DNA analysis (deltaF508/deltaF508, n=5; deltaF508/G542X, n=1). One case in which only one mutation had been recognised was diagnosed clinically after birth (deltaF508/unidentified mutation). Of the seven cases, none was diagnosed at 16-19 weeks, four at 16-24 weeks, and three after this. The incidence of heterozygous fetuses (15/209, 7%) was not significantly higher than the 5% expected in the general population. The mutations involved in these heterozygous cases were deltaF508 (n=13), G542X (n=1), and G551D (n=1).

CONCLUSIONS

Screening for cystic fibrosis should be offered to families in which fetal hyperechogenic bowel is diagnosed at routine ultrasonography. This underlines the need to review genetic counselling in this situation where the fetus is the index case for a genetic disease.

Costs, effects, and savings of screening for cystic fibrosis gene carriers

STUDY OBJECTIVE

Evaluating the costs, effects, and savings of several strategies for cystic fibrosis (CF) gene carrier screening.

DESIGN

A general model for evaluating prenatal, preconceptional, school, and neonatal carrier screening was constructed. For prenatal and preconceptional screening, two strategies were evaluated: single entry and double entry two step couple screening. Firstly, the Dutch situation was evaluated prospectively; subsequently the results were generalised to other carrier frequencies.

SETTING

Prospective simulation model.

MAIN RESULTS

Of all screening strategies, neonatal carrier screening gives most carrier couples an informed choice concerning reproduction. If the parents of carrier newborns would not be tested however, prenatal screening detects most carrier couples. Prenatal and single entry preconceptional screening programmes have a favourable cost-savings balance in the Netherlands under a wide range of assumptions. For double entry preconceptional screening and neonatal screening, high enough values of uptake of screening, prenatal diagnosis, and induced abortion are necessary. School carrier screening does not have a favourable cost-savings balance.

CONCLUSIONS

If a CF screening programme is judged to be useful on individual and social grounds, costs considerations are no obstacle for prenatal and single entry preconceptional screening.

Genetic advances in cystic fibrosis: to screen, to treat or both?

Since the identification of the cystic fibrosis (CF) gene in 1989 there have been considerable advances in treatment and fierce debate concerning CF screening programmes. Cystic fibrosis imposes a burden of suffering, of onerous treatment and of reduced lifespan. New emerging treatments are very expensive but are expected to improve survival and quality of life. Treatments and screening programmes should not be played off against one another in choices for funding. This paper presents an argument for the appropriate use of newer treatments which could be funded from savings arising from the effects of widespread implementation of newborn and active cascade carrier detection programmes. Newborn screening delays the need for expensive treatments reserved for those with advanced disease, by reducing pre-diagnosis tissue damage and the rate of progression of the disease. Carrier screening has the capacity to decrease the numerical burden of affected children born and increases the number of children born free of disease. For the present, carrier screening in the absence of a family history could be funded by the individuals who wish it or by those prepared to buy this service. All types of screening presume quality control, an existing laboratory and counselling infrastructure and an established method of communicating results.

Influence of five years of antenatal screening on the paediatric cystic fibrosis population in one region

BACKGROUND

Antenatal screening for cystic fibrosis has been endorsed by the US National Institutes of Health. Edinburgh is the only city in the UK with an established routine antenatal screening programme for cystic fibrosis.

AIMS

To report the change in numbers of infants diagnosed with cystic fibrosis born in Edinburgh after the introduction of antenatal screening for the disease.

POPULATION

Infants diagnosed as having cystic fibrosis (by sweat test or genotyping, or both) in the seven years before antenatal testing (1984-90) and the first five years of antenatal testing (1991-95). Children born in this region who had moved before diagnosis were identified from the UK cystic fibrosis survey database.

RESULTS

The incidence of cystic fibrosis decreased from an average of 4.6 to 1.6 children each year with antenatal screening. The reduction in the incidence (65%) was greater than that accounted for by prenatal diagnosis and termination (36%). Of the eight children born with cystic fibrosis during the period of antenatal screening, five had been subject to antenatal screening: three had only one mutation identified, one was missed due to a laboratory error, and one was identified as a one in four risk, but prenatal diagnosis was not performed.

CONCLUSIONS

Antenatal testing for cystic fibrosis has successfully reduced the incidence of cystic fibrosis in this region. Although the numbers are small, it is possible that the reduction in numbers may have been greater than might be expected from antenatal screening alone.

Carrier screening for cystic fibrosis: test acceptance and one year follow-up

We identified 124 carriers among 4,879 patients of prenatal care providers in the Rochester region. Six factors were identified that together permitted a correct classification regarding test acceptance for 77.5% of all subjects. For those pregnant, the most influential of these factors was a more accepting attitude toward abortion. As an indication for abortion, cystic fibrosis (CF) ranked between mild and moderate mental retardation. Of the 124 carrier women identified, we obtained 1-year follow-up information on 100. Mean score for CF knowledge at 1 year (77.4 +/- 13.2%), although significantly lower than immediately after counseling (84 +/- 12.4%), was still significantly higher than after detection but before counseling (51.1% +/- 20.7%). Anxiety about having a child with CF significantly declined from 25.8 +/- 8.0 SD immediately after counseling to 18.9 +/- 7.8 at 1 year (Spielberger State Anxiety Scale). Although 15 carriers regretted having been tested, 83% believed that they benefited from testing, 83% would make the same decision to be tested over again, and 79% would recommend testing to a friend. We conclude that, for most women, CF carrier screening accomplished its purpose: most carriers detected came for counseling, had their partners tested, and, if their partners were also carriers, had prenatal diagnosis. The major undesirable outcomes were that many women testing negative did not understand that a negative result did not exclude being a carrier and that three women found to be carriers did not have their partners tested because of anxiety or the unacceptability of pregnancy termination and therefore may not have carefully considered their decision to be tested. Both of these undesirable outcomes could have been avoided by greater attention to pretest patient education by the primary care provider.

Prenatal screening for cystic fibrosis carriers: does the method of testing affect the longer-term understanding and reproductive behaviour of women?

A comparative study of women who underwent prenatal cystic fibrosis (CF) carrier screening by either the 'two-step method' or the 'couple method' was carried out 2-4 years after testing. Recall of the screening test and test result, understanding of the implications of the test result, and reproductive intentions and behaviour were compared. Women screened by the two-step method were significantly better informed on the genetic implications of the test result and the significance of being a single gene carrier than their couple screen counterparts. Regardless of the method of screening, a majority of those who had received a negative test result erroneously believed that they were definitely not a carrier. However, women who intended having further children were significantly more likely to understand correctly that a negative test result meant that they were unlikely to be a CF carrier. The method of testing had no influence on reproductive intentions or behaviour. Differences in emphasis, content and presentation of pre-screening information and counselling between the two methods of screening are identified. Reasons for variation in the long-term understanding between women screened by the two methods are discussed.

PCR-based screening for cystic fibrosis carrier mutations in an ethnically diverse pregnant population

As the most common lethal autosomal recessive disorder in North America, cystic fibrosis (CF) is an obvious candidate for general population carrier screening. Although the identification of the causative gene has made detection of asymptomatic carriers possible, the extreme heterogeneity of its mutations has limited the sensitivity of the available DNA screening tests and has called into question their utility when they are applied to patients with no family history of the disease. The purpose of this study was to determine the technical feasibility, patient acceptance and understanding, and psychosocial impact of large-scale CF carrier screening in an ethnically diverse pregnant population. A total of 4,739 pregnant women attending prenatal clinics located in both an academic medical center and a large HMO were invited in person to participate. Of this group, 3,543 received CF instruction and assessments of knowledge and mood, and 3,192 underwent DNA testing for the six most common CF mutations, by means of a noninvasive PCR-based reverse-dot-blot method. Overall participation rates (ranging from 53% at the HMO to 77% at the academic center) and consent rates for DNA testing after CF instruction (>98%) exceeded those of most other American studies. The PCR-based screening method worked efficiently on large numbers of samples, and 55 carriers and one at-risk couple were identified. Understanding of residual risk, anxiety levels, and overall satisfaction with the program were acceptable across all ethnic groups. Our strategy of approaching a motivated pregnant population in person with a rapid and noninvasive testing method may provide a practical model for developing a larger CF screening program targeting appropriate high-risk groups at the national level, and may also serve as a paradigm for population-based screening of other genetically heterogeneous disorders in the future.

Carrier screening for cystic fibrosis in primary care: evaluation of a project in South Wales. The South Wales Cystic Fibrosis Carrier Screening Research Team

Population carrier screening for cystic fibrosis (CF) was offered to all patients aged 16-45 in one general practice in South Wales, excluding those in couples with a current pregnancy. Out of 1553 patients in this group, 481 subjects were tested, giving an overall uptake rate of more than 30%. The rate of uptake varied with the mode of invitation. Twenty-six carriers were identified, giving a prevalence of identified carriers of 5.4% (1 in 18.5) for those with no family history of CF. A further 18 carriers were identified by cascade testing of these 26. We describe the practical difficulties encountered in setting up this programme in primary care in South Wales. Questionnaires were administered or distributed to all subjects before and after testing. The response rate for the pre-test questionnaire was 95%, and 40-50% for the post-test questionnaires. These showed that, at 3 months post-test, 1 in 4 screen-negative subjects did not appreciate that they had a residual risk of being a carrier. At the same time, 15% of this group thought that there was a 1 in 4 chance of a child being affected if one parent was screen-positive (carried an identified mutation) and the other was screen-negative, and 40% thought there was no risk. Anxiety in relation to testing did not appear to be a major problem, although individual patterns of response to carrier status varied widely and more sensitive indicators of psychosocial impact of genetic tests are required. A pilot study of couple screening showed that this approach is unlikely to be useful in primary care, although we did not assess couple testing during pregnancy. For any programme of CF carrier screening to be established in primary care, it will be necessary to involve the primary care team from the earliest planning stage, so that the opportunity costs, training needs and other costs of the programme can be fully resourced.

Antenatal screening for cystic fibrosis

OBJECTIVE

To assess the practicality of implementing antenatal screening for cystic fibrosis in Yorkshire.

DESIGN

Prospective study in which all pregnant women were offered testing for the delta F508 mutation which accounts for about 85% of carriers in Yorkshire. The reproductive partners of those found to be cystic fibrosis carriers were then tested and any carrier referred for genetic counselling.

SETTING

Antenatal clinics in two hospitals and eight general practices.

POPULATION

Six thousand and seventy-one pregnant women.

RESULTS

A total of 3773 women (62%) accepted the screening offer. This was a lower uptake rate than in other published UK studies: Aberdeen (85-91%), Manchester (85%), Edinburgh (76-84%) and Oxford (67%). Nonetheless there were large and statistically significant differences in the uptake rate between centres within the study: 78% and 60% for the two hospitals and 67% for the general practices. One hundred and thirty women (3.4%) were found to be carriers and three carrier couples were identified. The median time interval for the laboratory to produce a result was five days and the cost was pounds 16 on average.

CONCLUSIONS

Antenatal screening for cystic fibrosis does not pose any special practical difficulties. It would be feasible to introduce it into routine practice in Yorkshire.

Psychological impact of population-based carrier testing for cystic fibrosis: 3-year follow-up. UK Cystic Fibrosis Follow-Up Study Group

BACKGROUND

The objective of this study was to show the long-term psychological effects of population-based screening for cystic fibrosis.

METHODS

The sample comprised all carriers (n = 435) and, for each carrier, two matched screen-negative individuals (n = 870) detected during screening programmes for cystic fibrosis in the general population and in antenatal populations carried out a median of 3 years earlier in six UK centres. Questionnaires were sent to all eligible participants, with reminders sent to non-responders. The main endpoints were understanding of test results, degree of anxiety, perceptions of health, and reproductive intentions, and behaviour.

FINDINGS

746 (62%) of 1201 questionnaires were returned. Recall of the meaning of test results was accurate in 225 (80%) of 280 carriers but only 200 (43%) of 466 screen-negative individuals. 46 (16%) of 280 proven carriers believed that their result meant that they were only likely, rather than definitely, to be a carrier; 232 (50%) of 466 of those with a screen-negative result erroneously believed that the result meant that they were definitely not carriers. There was no significant difference between carriers and screen-negative individuals in degree of general anxiety, although 16% of carriers reported feeling worried about their test results. Carriers had a poorer perception of their current health than did non-carriers, even though they had been told that carrier status confers no disadvantages to their own health. There were no differences between carriers and screen-negative individuals in reproductive intentions or behaviour.

INTERPRETATION

We have shown that in the long-term, retention of the meaning of test results from cystic fibrosis screening is poor. Further research is needed to improve the performance of test-related counselling programmes to ensure that the main objectives of these programmes, to provide information on carrier status and to allow informed reproductive decisions, are met.

Couple-based prenatal screening for cystic fibrosis in primary care settings

This study examines a couple-based screening protocol for cystic fibrosis (CF) during pregnancy. The screening test is positive only when both partners carry an identifiable mutation. The risk for the fetus to be homozygous is 1 in 4, and definitive prenatal diagnostic testing can be offered. Between six and seven of every ten CF cases can be identified by testing for seven CF mutations. Couple screening for CF has not been evaluated in a decentralized health-care system. Office guides, informational materials, and consent forms were provided to 69 physicians in Maine. Women sent buccal samples to the study centre and brought sampling materials to their partners. Samples from both individuals were required. When a mutation was identified in the woman's sample, the partner's sample was tested. Screening results were reported to the physician. Standardized follow-up surveys were carried out in selected women, key office staff, and physicians. 1770 women and 1682 partners submitted samples. Testing was successfully completed for 1645 couples. Screening results were positive in one couple; the fetus was homozygous for CF. Physicians, office staff, and nearly all women were satisfied with the screening process. Couple screening for CF is feasible and acceptable in decentralized primary care settings.

The views of general practitioners on community carrier screening for cystic fibrosis

BACKGROUND

Recent developments in molecular genetics have made it possible to identify carriers of the cystic fibrosis (CF) mutation, regardless of family history, before they have an affected child. Using these techniques, population or 'community' carrier screening can offer informed reproductive choice to individuals and couples who would not otherwise know of their risk of having a CF child.

AIM

This study set out to assess the views of general practitioners (GPs) on community carrier screening for CF and to consider the factors that influence their willingness to offer it themselves.

METHOD

A self-administered questionnaires was sent to all 616 GPs in four areas of North Thames (West) Region.

RESULTS

Two-thirds of respondents indicated that identifying carrier couples to offer genetic counselling before conception was a very important benefit of community carrier screening. Two-thirds felt that general practice was the most appropriate place in which to offer it, and similar proportions that the most appropriate times to do so were when a close relative was diagnosed and when seeking family planning. About half wanted to offer community carrier screening themselves; this was related to experience with CF patients and CF carrier testing, and estimates of the numbers of CF carriers in the practice.

CONCLUSIONS

There is considerable support among GPs for community carrier screening for CF in general practice, particularly in the context of family planning services. Knowledge and experience of CF increase GPs' willingness to offer it themselves.

Cystic fibrosis carrier screening in two New South Wales country towns

OBJECTIVE

To assess the feasibility of offering community testing for carrier status of delta F508, a gene mutation associated with cystic fibrosis (CF).

DESIGN

Prospective pilot survey.

SETTING

General practice, the two main high schools and workplaces in the country towns of Young and Harden (combined population, 14,940; with 7707 people aged 16-55 years) in New South Wales (NSW).

PARTICIPANTS

Individuals aged 16 years and over.

MAIN OUTCOME MEASURES

Number of delta F508 carriers, test uptake rates, mode of learning about the testing, motivation for testing, retention of knowledge about CF, and test results and emotional effects of knowledge about carrier status.

RESULTS

We tested 610 people (8% of the population aged 16-55 years) and identified 47 carriers (20% of the expected number in the 7707 people aged 16-55 years). Testing in schools had the highest uptake. Retention of knowledge was high; all delta F508-positive individuals recalled their carrier status accurately. Anxiety was transient among carriers; over 90% of all respondents felt they had made the right decision to be tested.

CONCLUSIONS

We recommend community testing for carrier detection and suggest targeting those with a family history of CF and girls aged over 16 in high schools.

Planning the development of cystic fibrosis gene carrier screening

OBJECTIVES

It is now possible to test individuals to assess their cystic fibrosis gene carrier status and a range of strategies for screening the population have been piloted. The objective of this research was to develop a planning framework which health care planners and purchasers can use to assess the overall quantifiable outcomes and direct costs resulting from a year of alternative screening strategies and the ways costs and outcomes evolve over time. Beyond broader ethical and clinical considerations the information provided by such a framework is needed to support decisions surrounding the development of screening programmes.

DESIGN

Operational Research modelling techniques were used to develop the planning framework. To help illustrate the framework it was then used to assess the quantifiable outcomes and direct costs of three of the main alternative screening strategies: from antenatal clinics, '2-step' screening where females are tested first followed by a screening invitation to the partners of female carriers, and 'couple' screening where both partners must agree to be tested at the outset; and from primary practice clinics 'active' contact of attenders. Quantifiable outcomes are defined as the number of individuals informed of their carrier status and the number of carriers, carrier couples, and affected fetuses detected. Direct costs are those associated with the recruitment and testing of individuals and the subsequent counselling of any gene carriers or carrier couples identified. Results are based on services for a resident population of 250,000 at two time points, year one and a year at 'steady state'.

RESULTS

The resultant framework estimates the number of individuals tested using data on the size of the target population, the proportion of that population alerted to the screening service, and the proportion who agree to be tested when approached. Given service users, prevalence data are used to assess service outcomes. Given the number of individuals approached and the subsequent demands for services, service costs can be estimated. Preliminary results indicate that in the short-term health care purchasers and planners who favour screening are likely to opt for antenatal strategies. Although the high coverage of the primary practice strategy leads to high outcomes in year one, relative to the antenatal strategies, it also leads to very high costs. At 'steady state', cost and outcome differences between the strategies are less marked.

CONCLUSION

This paper provides a framework which can be used to provide information to support decision-making surrounding the development of screening services. The methodology fills an important void in the literature and complements research elsewhere by health economists and by geneticists and their research colleagues. Preliminary findings based upon use of the approach demonstrate the need for continued research to further refine and improve the methodology.

Prenatal screening for cystic fibrosis: 5 years' experience reviewed

BACKGROUND

Although several programmes of prenatal screening for cystic fibrosis have been completed and reported, there are still uncertainties about rates of take up and also about the action of parents identified as having a one-in-four risk of an affected child. I report 5 years' experience with the two-step and couple models of prenatal screening of cystic fibrosis.

METHODS

Screening has been available at two antenatal clinics in Edinburgh, UK, since January, 1992, first on a research basis and then routinely. 25,000 couples have been screened.

FINDINGS

Take-up rates for the two-step and couple models of delivery are very similar at about 70%. Take-up rates did not change when screening moved from a research to a routine service. Of 22 high-risk couples identified entirely through screening, 20 (91%) opted for prenatal diagnosis. Four couples returned for second and two for third monitored pregnancies. In all eight cases where affected fetuses were identified, pregnancy was terminated.

INTERPRETATION

These data remove one of the few remaining obstacles to a general implementation of prenatal screening for cystic fibrosis.

Cost effectiveness of antenatal screening for cystic fibrosis

OBJECTIVE

To estimate the cost effectiveness of different antenatal screening programmes for cystic fibrosis.

SETTING

Antenatal clinics and general practices in the United Kingdom.

DESIGN

Four components of the screening process were identified: information giving, DNA testing, genetic counselling, and prenatal diagnosis. The component costs were derived from the literature and from a pilot screening study in Yorkshire. The cost of a given screening programme was then obtained by summing the components according to the specific screening strategy adopted (sequential and couple), the proportion of carriers detected by the DNA test, and the uptake of screening. Baseline assumptions were made about the proportion with missing information on carrier status from previous pregnancies (20%), the proportion changing partners between pregnancies (20%), and the uptake of prenatal diagnosis (100%). Sensitivity analysis was performed by varying these assumptions.

MAIN OUTCOME MEASURE

Cost per affected pregnancy detected.

RESULTS

Under the baseline assumptions sequential screening costs between pounds 40,000 and pounds 90,000 per affected pregnancy detected, depending on the carrier detection rate and uptake. Couple screening was more expensive, ranging from pounds 46,000 to pounds 104,000. From the sensitivity analysis a 10% change in the assumed proportion with missing information from a previous pregnancy alters the cost by pounds 4000; a 10% change in the proportion with new partners has a similar effect but only for couple screening; and cost will change directly in proportion to the uptake of prenatal diagnosis.

CONCLUSIONS

While economic analysis cannot determine screening policy, the paper provides the NHS with the information on cost effectiveness needed to inform decisions on the introduction of a screening service for cystic fibrosis.

Frequency of common cystic fibrosis gene mutations in chronic bronchitis patients

It has been suggested that the delta F508 deletion, the most common mutation in the cystic fibrosis (CF) gene, might be linked to chronic bronchial hypersecretion. We investigated whether such an association could be found in chronic bronchitis, since chronic bronchial hypersecretion is an important and specific element of chronic bronchitis. We screened 100 patients hospitalized for chronic bronchitis with six of the most frequently occurring CF gene mutations: delta F508, R553X, G542X, G551D, N1303K, and 621-1G-->T. Only one patient affected by chronic bronchitis and diffuse bronchiectasis was heterozygous for the deletion delta F508; no other mutations were found. This is not significantly different from the expected frequency of CF carriers in northern Europe, which is 1 in 25. Thus, no association between the most commonly occurring cystic fibrosis genes and chronic bronchitis is likely to exist and routine screening of patients without further signs of cystic fibrosis would seem to be of no benefit in northern Europe.

Stepwise or couple antenatal carrier screening for cystic fibrosis?: women's preferences and willingness to pay

Several antenatal cystic fibrosis carrier screening trials have offered women testing by either the stepwise or the couple method. In this study, both approaches were described to women attending an antenatal clinic, who were then asked which method they preferred. An estimate of the value to women of each type of test was also ascertained using a "willingness to pay" (WTP) method. Of 450 women, 279 (62%) preferred stepwise screening, 117 (26%) preferred couple screening, and 54 (12%) had no preference. Mean WTP for stepwise screening was 19 pounds (95% CI 17.50 pounds-20.50 pounds), and that for couple screening was 18 pounds (95% CI 16.50 pounds-19.50 pounds). The majority of women preferred stepwise screening although the average WTP for each method was similar.

Cost comparison of different methods of screening for cystic fibrosis

OBJECTIVE

To compare the costs of several proposed methods of screening for cystic fibrosis.

SETTING

England and Wales.

METHODS

The costs of screening carried out at hospital antenatal clinics, general practitioner (GP) antenatal consultations, GP surgeries, and at work were estimated using data from demonstration projects. Couple screening, stepwise screening, and screening of individuals were considered.

RESULTS

Couple screening at antenatal hospital clinics was the least expensive per carrier couple detected, amounting to 35,700 pounds (142,900 pounds for each potential cystic fibrosis fetus detected). The costs of the reagents (25 pounds per test) accounted for over 60% of this total.

CONCLUSIONS

Antenatal screening, in addition to being the most cost effective method of screening, is also medically the screening method of choice as it provides information at the latest time when effective preventive action can be taken and at a time when all people to be screened are likely to be accessible. If the costs of the reagents could be reduced to 5 pounds (still higher than the costs of most diagnostic reagents) the cost for each pregnant carrier couple offered screening would be reduced by 50% to about 18,000 pounds, and the cost of offering screening to 684,000 pregnant couples in England and Wales would be about 9 1/2 m instead of 19 m pounds.

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.

A single-tube multiplex system for the simultaneous detection of 10 common cystic fibrosis mutations

We describe a nonisotopic single-tube polymerase chain reaction (PCR) multiplex system that detects 10 of the more common cystic fibrosis (CF) mutations (delta F508, delta I507, V520F, G551D, G542X, R553X, R117H, 621 + 1G-->T, N1303K, A455E). The use of this method detects approximately 90% of the CF alleles in the British population. Five exons of the CF gene are amplified simultaneously by PCR, followed by an overnight triple enzyme restriction digest, and then resolved by high-resolution gel acrylamide electrophoresis.

Carrier screening in the community

A number of different models of cystic fibrosis (CF) carrier screening have now been tested in pilot trials. Apart from opportunistic and cascade testing (which are strictly speaking not true forms of screening), the major programmes have been directed either to young adults in primary care or to pregnant women in antenatal clinics. Only in the latter form of screening has sufficient data been collected to allow conclusions to be reached on the optimum mode of delivery. It seems very probable that when CF carrier screening passes into routine service, it will be the antenatal couple model that is used.

Gene therapy for cystic fibrosis: will it affect the uptake of prenatal carrier screening?

We report a study which examined whether the decision of 135 couples to accept prenatal cystic fibrosis (CF) carrier screening would be influenced by the advent of gene therapy. A majority (91 couples; 67 per cent) felt that gene therapy for CF would not influence their decision to be screened. Twenty-two couples (16 per cent) stated that they would decline to be screened and an equal number felt ambivalent. Even if the life expectancy of a CF sufferer were increased by gene therapy to normal, 78 per cent of couples would still wish to avail themselves of prenatal carrier screening. A majority of women who decline screening do so because they are opposed to termination of pregnancy. The availability of gene therapy could increase the proportion of couples who accept screening.

Carrier screening for cystic fibrosis

A number of different models of CF carrier screening have now been tested in pilot trials. Apart from opportunistic and cascade testing (which are strictly speaking not true forms of screening), the major programmes have been directed either to young adults in primary care or to pregnant women in antenatal clinics. Only in the latter form of screening has sufficient data been collected to allow conclusions to be reached on the optimum mode of delivery. It seems very probable that when CF carrier screening passes into routine service, it will be the antenatal couple model that is used.

Laboratory screening for genetic disorders and birth defects

Screening for inherited disease is a preventative health measure that started in the 1960s with the development of programs for the detection of PKU in newborns and that has had a major impact on reducing the burden of disease. Developments in technology have led to the availability of large scale testing for an increasing number of both acquired and genetic disorders. Laboratory testing is only one facet of a screening program and consideration should be given to availability of testing to all individuals, education regarding the program, effectiveness of treatment, long-term benefits both for individuals and society, ethical issues, and cost benefits. In this review, newborn, prenatal, and heterozygote screening are discussed.