Cystic fibrosis heterozygote screening in 5,161 pregnant women.

A screening program for cystic fibrosis (CF) heterozygotes was conducted in a large HMO prenatal population, to evaluate the level of interest among eligible patients, the effectiveness of prescreening education, attitudes toward the screening process, psychological effects, and utilization of prenatal diagnosis and its outcomes. The heterozygote identification rate and frequency of specific CFTR mutations were also assessed. Identified carriers were offered genetic counseling and testing of male partners. Prenatal diagnosis was offered if both parents were identified as carriers. A total of 5,161 women underwent carrier testing; 947 others completed survey instruments only. The acceptance rate of screening was high (78%), and pretest education by videotape was generally effective. Adverse psychological effects were not reported. Participants generally found screening to be desirable and useful. Screening identified 142 female heterozygotes, 109 couples in which the male partner was not a carrier, and 7 high-risk couples. The incidence of R117H mutations was much higher than expected. The number of identified carriers was much lower in Hispanics than in Caucasians. We conclude that large-scale prenatal screening for CF heterozygotes in the absence of a family history of CF is an acceptable method for identifying couples at risk for affected fetuses. Sufficient pretest education can be accomplished efficiently, test insensitivity is well accepted, adverse psychological events are not observed, and general patient satisfaction is high.     

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.     

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.     

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.     

Carrier screening for cystic fibrosis in a prenatal setting

Maternal prenatal cystic fibrosis (CF) screening was offered from September, 1997, to April, 1999, at the Ghent University Hospital, to couples undergoing prenatal diagnosis (amniocentesis) for reasons not related to CF. Fifteen minutes were devoted to explaining CF, CF screening, and the study protocol. The purpose was to assess the short- and long-term knowledge of CF, the attitude towards carrier screening, and carriership. A total of 314 couples entered the pilot study; 13 female CF carriers were identified. None of their partners carried an identifiable mutation. Our survey results show that information about CF and CF screening can be given effectively as part of antenatal care because most couples recalled important medical and genetic issues, valued the genetic test for CF, and seemed to cope well with the results. Risk estimates and actual numbers were more difficult to process and recall. From the small number of couples in which the woman alone was found to be a carrier, there was little or no evidence of marked distress.     

Cystic fibrosis carrier testing in early pregnancy by general practitioners.

OBJECTIVE--To assess the feasibility of genetic counselling in general practice by using cystic fibrosis carrier screening at the booking appointment as an integral part of routine antenatal care and as a paradigm for the wider participation of general practitioners in medical genetics. DESIGN--Maternal testing (male partner tested only if woman screens positive) and couple testing for cystic fibrosis carrier status in the antenatal population attending one general practice and, later, in a further six (outreach) practices also. SETTING--Two partner urban training practice (pilot practice) in south Manchester, and six north west practices (two inner city, three urban, one rural dispensing). SUBJECTS--Total practice population of 50,000 (pilot practice plus six outreach practices) with an estimated 500-800 pregnancies per year. MAIN OUTCOME MEASURES--(a) Proportion of carriers of cystic fibrosis identified, counselled, and appropriately managed within the first trimester of pregnancy; (b) questionnaire and interview measures of patient satisfaction and stress. RESULTS--Eleven carriers of cystic fibrosis were detected including one carrier couple. This carrier couple, after extensive counselling, elected to have prenatal diagnosis by chorionic villus biopsy. The fetus was homozygous normal. CONCLUSIONS--General practitioners can successfully integrate genetic counselling and cystic fibrosis carrier screening into the first antenatal booking appointment. When a carrier couple is identified clinical geneticists can help with the discussion of reproductive options, and prenatal diagnosis by chorionic villus biopsy can be completed within the first trimester. The results suggest that general practitioners will have an increasingly important role in medical genetics, subject to continuing evaluation of patient acceptability and stress.     

Cystic fibrosis carrier population screening in the primary care setting.

To determine the receptivity of prenatal care providers and their patients to carrier testing for cystic fibrosis (CF), we offered free carrier screening, followed by genetic counseling of carriers, to all prenatal care providers in Rochester, NY, for all their female patients of reproductive age, pregnant or not. Of 124 prenatal care providers, only 37 elected to participate, but many of these offered screening only to pregnant women. The acceptance rate among pregnant women was approximately 57%. The most common reasons for accepting screening were to obtain reassurance (50.7%) and to avoid having a child with CF (27.8 %). The most common reasons for declining screening were not intending to terminate a pregnancy for CF (32.4%) and believing that the chance of having a CF child was very low (32.2%). Compared with decliners, acceptors were more likely to have no children, regarded having a child with CF as more serious, believed themselves more susceptible to having such a child, knew more about CF, would be more likely to terminate a pregnancy if the fetus were shown to have CF, and more strongly supported offering CF screening to women of reproductive age. Of 4,879 women on whom results were obtained, 124 were found to be carriers. Of these 124 carriers, the partners of 106 were tested. Of the five at-risk couples, four requested prenatal diagnosis and one requested neonatal diagnosis. No woman found to be a carrier whose partner tested negative requested prenatal diagnosis. Except for the imperfect knowledge of those testing negative, none of the adverse outcomes predicted for CF carrier testing in the general population were observed in this study.     

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.     

Prevention of homozygous beta-thalassemia by carrier screening and prenatal diagnosis in Sardinia.

We report here results of a 3-year pilot voluntary screening program coupled with prenatal diagnosis directed to the prospective prevention of homozygous beta-thalassemia (beta-thal) in Sardinia. The screening program took two approaches: outreach community testing and hospital testing on request after a period of sensibilization. The outreach testing was very effective as, taking into account the already known number of couples at risk with an affected proband (20), 74% of the couple at risk expected (61) on the basis of the carrier rate were identified. Less effective was the hospital testing in which half of the couples at risk expected were detected (502 with the 199 without an affected proband). After nondirective genetic counseling, approximately 85% of the couples at risk, which had a pregnancy, with no statistically significant difference between those with and those without a proband, requested prenatal testing. This figure showed a steadily increase from the beginning in 1977 to 1980. All the pregnancies (42), but two carrying homozygous fetuses, were terminated on parental request. A continuous hospital survey of thal-major admissions in the different hospitals of the counties showed a steady decline in the incidence figure at birth from 1976 (1:213) to 1978 (1:290). These results showed that even in a medium-developed, rural, Catholic population screening coupled with prenatal diagnosis can be successful in the control of a fatal, recessively inherited disorder.     

Carrier screening for Gaucher disease in couples of mixed ethnicity

With the advent of mutational analysis for Gaucher disease, carrier screening has been incorporated into many Jewish genetic disease screening programs. Frequencies and mutations for Gaucher disease in non-Jewish populations are less well established and the detection rate of carriers are lower. Testing is problematic for resolving residual risk in a couple of mixed ethnicity. We report the testing choices made by 20 consecutive couples of mixed ethnicity where the Ashkenazi Jewish partner was identified to be a Gaucher disease gene carrier. Carrier studies of the non-Jewish partner were elected as follows: DNA studies alone, 5 (25%); enzymatic assay, 2 (10%); both, 6 (30%); no carrier studies, 7 (35%). Of the 7 couples not electing carrier studies, one was not in a pregnancy and 6 elected prenatal diagnosis in lieu of parental testing by enzymatic analysis of amniocytes. One couple elected parental carrier studies as well as prenatal diagnosis. All couples electing prenatal Gaucher determination had amniocentesis for other indications as well (4, advanced maternal age; 4, parental anxiety). We conclude that Gaucher screening is feasible for couples of mixed ethnicity if appropriate counseling and testing are offered.     

Screening for carriers of cystic fibrosis--a general practitioner's perspective.

The identification of the gene for cystic fibrosis has led to the possibility of population based screening for carriers of cystic fibrosis to identify couples at risk of having an affected child. Pilot studies have shown that screening is feasible and does not cause untoward anxiety, though the uptake of testing varies considerably with the setting and method of invitation. Screening offered at times when individuals (and health professionals) perceive it as directly relevant will probably gradually become established in the United Kingdom. This review examines the role of general practice in genetic carrier screening as exemplified by cystic fibrosis. General practice has a pivotal role from the beginning in providing individuals and couples with information, facilitating testing of patients'' relatives and of carriers identified by screening elsewhere (such as antenatal clinics), and offering testing in the context of reproduction. Screening for the cystic fibrosis gene will probably be followed by other genetic screening programmes.     

Preconception cystic fibrosis carrier couple screening: impact,understanding, and satisfaction

The impact, understanding of test-results, and satisfaction among participating couples in a preconception cystic fibrosis (CF) carrier screening project were assessed 6 months after testing. Questionnaire data were obtained from 17/18 identified carriers, 15 partners of carriers with negative test results, and 794 (73%) other participants. None of the carriers changed their reproductive plans because of their test results. Eight participants were worried about their results, including four carriers. Those who attended a general practitioner (GP) consultation for pretest education were less worried than those who attended an educational session. Seven carriers felt less healthy. Predictors of a correct understanding of test results (correct in 62% of participants) were: positive test results, high level of knowledge of CF, high level of education, attending an educational session, and previously heard of CF. All participants who reported that they were worried, all carriers, and 95% of the other participants said that they would make the same decision to be tested again. Although couples who were educated during a GP consultation were less worried, the results of the study suggest that understanding is more correct in couples attending an educational session. The results further suggest that since satisfaction with the screening was high, worries and feeling less healthy due to the test results are probably not a great burden.     

Carrier screening for beta-thalassemia during pregnancy in India: a 7-year evaluation

AIM: Premarital screening for beta-thalassemia is not widely acceptable in India; hence, we evaluated the effectiveness of antenatal screening and counseling over 7 years. METHODS: 61,935 pregnant women were screened using the single-tube osmotic fragility test during their first antenatal visit. Individuals who were positive were investigated further for diagnosis of beta-thalassemia and other abnormal hemoglobins. Spouses of carrier women were tested whenever available. Couples at risk were given the option of prenatal diagnosis. RESULTS: Only 19% of the women registered at the antenatal clinic in the first trimester of pregnancy, and 14% of the women were positive per the osmotic fragility test; 1020 beta-thalassemia heterozygotes and 213 women with other hemoglobinopathies were identified, majority being in the second and third trimesters. Seven hundred and thirteen (69%) of their husbands could be tested, and 37 couples at risk were identified. Only 15 couples had a prenatal diagnosis done. Four couples with affected fetuses opted for termination of pregnancy. The remaining couples either did not respond after counseling or the pregnancies were advanced for prenatal intervention. CONCLUSION: This first large study shows that antenatal screening is acceptable in India; however, awareness generation is still a primary requisite to make women register early at antenatal clinics and bring their spouses for screening when required.     

Twenty-year outcome analysis of genetic screening programs for Tay-Sachs and beta-thalassemia disease carriers in high schools.

Programs for education, screening, and counseling of senior-high-school students, in populations at high risk for Tay-Sachs and beta-thalassemia diseases, have existed for >20 years in Montreal. Four process and outcome variables are reported here: (i) voluntary participation rates in the high-school cohort; (ii) uptake rates for the screening test; (iii) origin of carrier couples seeking the prenatal diagnosis option in the programs; and (iv) change in incidence of the two diseases. Between 1972 and 1992, we screened 14,844 Ashkenazi-Jewish students, identified 521 HexA-deficient carriers (frequency 1:28), reached 89% of the demographic cohort in the educational component of the program, and achieved 67% voluntary participation in the subsequent screening phase. The corresponding data for the beta-thalassemia program are 25,274 students (mainly of Mediterranean origin) representing 67% of the cohort with 61% voluntary participation in the screening phase (693 carriers; frequency 1:36). From demographic data, we deduce that virtually all the carriers identified in the high-school screening program remembered their status, had their partner tested if they did not already know they were a carrier couple, and took up the options for reproductive counseling/prenatal diagnosis. In Montreal, the current origin of all couples using prenatal diagnosis for Tay-Sachs and beta-thalassemia diseases is the corresponding genetic screening/testing program, whereas, at the beginning of the programs, it was always because there was a history of an affected person in the family. Incidence of the two diseases has fallen by 90%-95% over 20 years; the rare new cases are born (with two exceptions) outside the target communities or to nonscreened couples.     

Preconceptional cystic fibrosis carrier screening: opinions of general practitioners, gynecologists, and pediatricians in the Netherlands

Knowledge of the opinions of physicians with regard to preconceptional cystic fibrosis (CF) carrier screening and the possible factors that are associated with their opinions is important for the implementation of such a screening program. Data were obtained from a study in which genetic knowledge, opinions with regard to genetic testing and related skills were investigated. A questionnaire, developed and used by American researchers, was adapted to the Dutch health care situation, and sent to randomly selected general practitioners (GPs) (n = 200), gynecologists (GYNs) (n = 300), and pediatricians (PEDs) (n = 265). In this part of the study, their opinions with regard to genetic preconceptional CF carrier screening in different situations were assessed. The response rate for the GPs, GYNs, and PEDs was 64%, 69%, and 72%, respectively. In total, 63% of the GPs, 69% of the GYNs and 72% of the PEDs supported preconceptional CF carrier testing if a couple requested a test. Sixteen percent, 19% and 25%, respectively, were in favor of actively offering a test with 95% test sensitivity to all couples who were planning a pregnancy. A positive opinion on preconceptional CF carrier screening was associated with the following variables: "considering the test sensitivity as less important" (GPs, GYNs), "high perceived risk of having a child with CF" (GYNs), "providing genetic counselling in their own practice" (PEDs) and "reassurance when both partners test negative" (PEDs). Physicians are sympathetic toward preconceptional CF carrier screening if the couples themselves request a test. Physicians had reservations about routinely offering a CF carrier test.     

Targeted extended cystic fibrosis mutation testing on known and at-risk patients and relatives

This paper reports mathematically derived residual risks of being a carrier or being affected with cystic fibrosis following various screening scenarios to assist in interpreting test results and advising patients. While parental screening with 23 American College of Medical Genetics (ACMG) cystic fibrosis mutations defines the 64% of affected U.S. Caucasian fetuses with two detectable mutations, newborn screening for elevated immunoreactive trypsinogen (IRT) and sweat chloride identifies an additional 36% of affected newborns with zero or one detected mutation. The relatives of these affected newborns with less than two detectable mutations have higher posterior (after) 23 mutation-negative test risks of carrying undetected mutations. These calculations emphasize how knowledge of the mutations in the related affected patient substantially improves upon the quality of after-test advice to patients. Furthermore, negative tests of the partner without a family history and/or more extensive cystic fibrosis transmembrane conductance regulator (CFTR) gene testing also increases the likelihood that a negative report is truly negative. When a newborn patient with zero or one detected CFTR mutation has an inconclusive sweat test result, the sweat test should be repeated before ordering additional often unnecessary CFTR gene sequencing. Given the same composite mutation panel test accuracy, a higher proportion of reported test results would be correct during parental screening than when testing at-risk fetuses or symptomatic newborns. Prenatal and newborn screening would be enhanced substantially by medical professionals offering copies of all positive parental and newborn test reports to the parents to share with their relatives. These principles are likely to be applicable to other genetic diseases as the most common mutation frequencies are reported.     

Metachromatic leukodystrophy in the habbanite Jews: high frequency in a genetic isolate and screening for heterozygotes.

A very high incidence of late infantile metachromatic leukodystrophy (MLD) (1/75 live births) was found in the Jewish Habbanite community which constitutes a genetic isolate of about 1,000-1,200 individuals. Screening in this population for aryl sulfatase A (ASA) levels in married adults revealed a carrier frequency for MLD of 17% and identified six couples of whom both partners were heterozygotes (6% of screened couples). In three pregnancies of these couples, prenatal diagnosis for the detection of ASA in the fetus was performed.     

Lack of interest by nonpregnant couples in population-based cystic fibrosis carrier screening.

We used signs and letters to offer free cystic fibrosis (CF) carrier screening to nonpregnant adults in stable relationships who visited numerous clinical and nonclinical sites in Nashville. A total of 179 individuals (<<1% of those eligible) elected to be tested. To understand this observation, we used questionnaires to assess individuals' attitudes about genetic testing in general and about CF carrier screening in particular (n=873). Participants expressed conflicting views about carrier screening. More than 90% of people thought that genetic testing should at least be available. Most respondents said that the views of their partners and physicians were important in their decision making, and most believed that these others favored genetic testing. Yet, more than two-thirds indicated that such factors as insurability, being "at risk," what they would need to learn, abortion, and religious beliefs were important in their decision making, opinions that mitigated against genetic testing. In particular, one-third feared that carriers would lose their health insurance, one-quarter said that they would have been more interested had they been able to provide DNA by buccal swab rather than by finger stick, and less than one-sixth believed that genetic testing was meddling in God's plan. In the face of both the low level of use of free CF carrier screening by nonpregnant couples when it was not offered in person by health-care professionals and the wide variety of concerns demonstrated, we believe that clinicians should not routinely offer carrier screening to nonpregnant individuals who do not have a family history of CF.     

Uptake of cystic fibrosis testing in primary care: supply push or demand pull?

OBJECTIVE--To determine the acceptability and feasibility of screening for carriers of cystic fibrosis in a primary care setting. DESIGN--Follow up study over 15 months of patients offered carrier testing by mouthwash. SETTING--A general practice in inner London. SUBJECTS--5529 patients aged 18-45 invited by various methods and combinations of methods (letter, booklet, personal approach) for testing. MAIN OUTCOME MEASURES--Uptake of screening, anxiety, and knowledge of test. RESULTS--957 (17%) invitees were screened over the 15 months. 28 carriers and no carrier couples were detected. Uptake rates were 12% (59/502 patients) among patients invited by letter and tested by appointment; 9% (47/496) among patients invited by letter, with leaflet, and tested by appointment; 4% (128/2953) among patients invited by letter six weeks before the end of the study and tested by appointment; 17% (81/471) among patients offered passive opportunistic testing; 70% (453/649) among patients offered active opportunistic testing; and 25% (22/88) among patients offered active opportunistic testing by appointment. A short term rise in anxiety among those given a positive test result had dissipated by three months. At three months about one fifth and one third of those given positive and negative results respectively did not understand their results correctly. CONCLUSION--These results suggest that the strongest variable in determining uptake of screening is the active approach by a health professional offering immediate testing. It remains to be resolved whether the high uptake rates achieved by active recruitment indicate a supply push for this new test rather than a demand from the population.