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

Prenatal maternal plasma DNA screening for cystic fibrosis: A computer modelling study of screening performance

Background: Prenatal cystic fibrosis (CF) screening is currently based on determining the carrier status of both parents. We propose a new method based only on the analysis of DNA in maternal plasma. Methods: The method relies on the quantitative amplification of the CF gene to determine the percentage of DNA fragments in maternal plasma at targeted CF mutation sites that carry a CF mutation. Computer modelling was carried out to estimate the distributions of these percentages in pregnancies with and without a fetus affected with CF. This was done according to the number of DNA fragments counted and fetal fraction, using the 23 CF mutations recommended by the American College of Medical Genetics for parental carrier testing. Results: The estimated detection rate (sensitivity) is 70% (100% of those detected using the 23 mutations), the false-positive rate 0.002%, and the odds of being affected given a positive screening result 14:1, compared with 70%, 0.12%, and 1:3, respectively, with current prenatal screening based on parental carrier testing. Conclusions: Compared with current screening practice based on parental carrier testing, the proposed method would substantially reduce the number of invasive diagnostic procedures (amniocentesis or chorionic villus sampling) without reducing the CF detection rate. The expected advantages of the proposed method justify carrying out the necessary test development for use in a clinical validation study.

Genetic screening in 2,710 infertile candidate couples for assisted reproductive techniques: results of application of Italian guidelines for the appropriate use of genetic tests

OBJECTIVE

To report the results of the routine application of Italian guidelines that apply to infertile patient candidates for any assisted reproduction technique (ART). The guidelines recommend performing a karyotype analysis in each couple and the screening test for mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) in one of the two partners.

DESIGN

Case series.

SETTING

Infertility unit.

PATIENT(S)

Two thousand seven hundred ten consecutive infertile couple candidates for ART.

INTERVENTION(S)

Peripheral blood evaluation of karyotype and CFTR gene.

MAIN OUTCOME MEASURE(S)

Frequency of aberrant karyotype and mutated CFTR gene.

RESULT(S)

A total of 74 aberrant karyotypes were diagnosed, corresponding to 1.3% (95% confidence interval [CI], 0.9%-1.7%) in women and to 1.5% (95% CI, 1.0%-2.0%) in men. In men, the frequency of chromosomal abnormalities differed according to the treatment group (0.3%, 1.1%, and 2.2% in IUI, IVF, and ICSI, respectively). The same was not observed in women. Excluding the 5T variant, 3.8% of the screened patients showed a mutated CFTR gene (95% CI, 3.1%-4.5%), and the mutation was found in both partners in 0.2% of the couples (95% CI, 0.0-0.4%).

CONCLUSION(S)

The frequency of aberrant karyotypes is higher in infertile couples than in the general population, whereas the frequency of a mutation of the CFTR gene is similar.

Developing and optimizing a decisional instrument using self-reported ancestry for carrier screening in a multi-ethnic society

PURPOSE

To develop a decisional instrument for ancestry-based cystic fibrosis and/or hemoglobinopathies carrier couple screening in The Netherlands.

METHODS

A flowchart (Instrument A) and a questionnaire with maps of geographical areas with originally high cystic fibrosis and hemoglobinopathies carrier frequencies (Instrument B), were developed to support participants in self-assessing their eligibility as a couple for carrier screening for cystic fibrosis and/or hemoglobinopathies. The outcome was compared to the self-reported origin of both partners' ancestors during an in-depth interview. Furthermore, preference for Instrument A or B was determined.

RESULTS

Of the 112 participants, 88% (99/112, 95% CI 82-94%) (Instrument A) and 91% (102/112, 95% CI 86-96%) (Instrument B), respectively, arrived at a decision in accordance with their ancestral origin, and 57% (64/112, 95% CI 48-66%) preferred Instrument B. A false negative proportion of 5.5% suggests that some carriers will exclude themselves from screening. Results might improve with minor changes in the instruments with regard to geographic specification, and availability of translated versions.

CONCLUSION

A decisional instrument to assess ancestry-based eligibility for cystic fibrosis and/or hemoglobinopathies carrier screening, is now available and can with slight adaptations be used in other countries. The instrument also takes into account the possibility of mixed ancestry.

Cystic fibrosis prenatal screening in genetic counseling practice: recommendations of the National Society of Genetic Counselors

For over a decade, prenatal screening for cystic fibrosis (CF) has been considered a model for the integration of genetic testing into routine medical practice. Data from pilot studies and public policy discourse have led to recommendations by some professional organizations that CF screening should be offered or made available to pregnant women and their partners, and to couples planning a pregnancy. It is crucial that genetic counselors gain thorough understanding of the complexities of CF and the implications of positive test results, so that they may serve as a reliable, educated referral base and resource for health care providers and their patients. While not all pregnant women will be referred for genetic counseling prior to CF carrier testing, genetic counselors often will be asked to counsel clients after they have a positive test result, or who are found to be at increased risk. Genetic counselors can play an important role in providing accurate and current information as well as support for patients' informed decisions. These recommendations were created by a multicenter working group of genetic counselors with expertise in CF and are based on personal clinical experience, review of pertinent English language medical articles, and reports of expert committees. The recommendations should not be construed as dictating an exclusive course of management, nor does the use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Practice patterns of obstetrician-gynecologists regarding preconception and prenatal screening for cystic fibrosis

OBJECTIVE

To assess practices of obstetrician-gynecologists regarding carrier screening for cystic fibrosis (CF).

METHODS

A questionnaire investigating practice patterns and opinions pertaining to CF screening was mailed to 1165 members of the American College of Obstetricians and Gynecologists (ACOG), of whom 565 participate in the Collaborative Ambulatory Research Network (CARN) and 600 were randomly selected.

RESULTS

Of the questionnaires, 64% were returned. Statistical analyses were limited to the 632 respondents whose primary medical specialty was gynecology (Gyn Only) or obstetrics and gynecology (ObGyn). CARN membership was not a significant factor on any nondemographic measure. Almost one-half of physicians do not ask nonpregnant patients their family history of CF or provide them with information about CF screening. The majority of ObGyns (88.7%) ask obstetric patients their family history of CF, and offer CF carrier screening. Almost two-thirds (65.8%) offer screening to all prenatal patients. Among those ObGyns who selectively offer CF screening to pregnant patients, only 27.4% utilized all of the selection criteria in the guidelines. Liability for not offering screening, familiarity with CF, and the ability to interpret a positive screening test were important physician concerns.

CONCLUSION

The results indicate a need for minimizing the complexity of clinical guidelines for population-based genetic screening, prospective assessment of implementation and focused continuing education for providers.

Fetal anomalies: ethical and legal considerations in screening, detection, and management

A number of ethical considerations arise with regard to screening for, detecting, and managing fetal anomalies. Some of these considerations involve the need to give attention to emotional distress the pregnant woman might be experiencing. The ethical principle of beneficence gives rise to a duty of the obstetrician to provide emotional support when needed in relation to screening, confirmatory testing, giving bad news, making abortion decisions, making management decisions after viability, and dealing with the grieving process. Other issues involve ethical decision-making, such as deciding what recommendations to make concerning management of fetal anomalies after viability. The ethical principle of autonomy creates a duty of the obstetrician to help the pregnant woman make informed management decisions based on her values and goals. A recommendation for a particular approach to management is sometimes ethically justifiable on the basis of an analysis of the risks and benefits to the mother and fetus. Legal considerations are relevant because they create requirements or prohibitions that must be taken into account in ethical decision-making. The discussion in this article does not exhaust the range of issues that arise. For example, sometimes a delivery procedure is considered that is traumatic to the fetus, such as cephalocentesis for vaginal delivery of a fetus with hydrocephaly. The reader is referred to other sources for a discussion of the ethics of delivery procedures that might injure or kill the fetus. Other issues involve deciding when there is a duty to offer new prenatal genetic tests, routinely or for high-risk couples, and whether to carry out maternal requests for prenatal tests for late-onset diseases and susceptibilities to diseases. These issues have been discussed elsewhere.

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.

Variables that underlie cost efficacy of prenatal screening

As genetic research and technology continues to expand, carrier testing for an increasing number of single gene disorders is becoming available. Tay-Sachs disease and cystic fibrosis are two common recessive conditions with large-scale health implications. Tay-Sachs disease was the first genetic disorder for which community-based screening efforts were utilized and has provided a foundation for the development of other screening programs. Cystic fibrosis testing, on the other hand, has additional complexities and the implementation of population-based screening has been under debate. The many issues (technical, educational, social, psychological and economical) which must be considered as preconceptional and prenatal genetic screening is incorporated into clinical practice are discussed here in the context of Tay-Sachs disease and cystic fibrosis.

Molecular diagnosis of cystic fibrosis

A review of the current molecular diagnosis of cystic fibrosis including an introduction to cystic fibrosis, the gene function, the phenotypic variation, who should be screened for which mutation, newborn and couple screening, quality assurance, phenotype-genotype correlation, methods and method limitations, options, statements, recommendations, useful Websites and treatments.

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.

Updated assessment of cystic fibrosis mutation frequencies in non-Hispanic Caucasians

PURPOSE

To update estimates of individual and cumulative cystic fibrosis (CF) mutation frequencies in non-Hispanic Caucasians for the prenatal screening panel recommended by American College of Medical Genetics and to determine the impact on screening performance.

METHODS

Two data sources were used. In the first (CF Genetic Analysis Consortium), our re-analysis was restricted to North American studies. In the second (CF Foundation National Patient Registry), we performed a new analysis restricted to individuals tested at eight Therapeutic Development Network sites.

RESULTS

The updated average cumulative proportion of mutations identified is 88.34% (higher than previously reported), indicating that 78% of high-risk couples (and affected fetuses) can potentially be identified.

CONCLUSION

Prenatal CF screening in U.S. non-Hispanic Caucasians is more effective than previously thought.

Genetic counseling after implementation of statewide cystic fibrosis newborn screening: Two years' experience in one medical center

PURPOSE

To study the follow-up of genetic counseling performed in families with a newborn detected with one cystic fibrosis (CF) mutation in a statewide newborn screening pilot program.

METHODS

Newborns in Massachusetts with an elevated trypsinogen level on newborn screen who are found to have one mutation for CF on a selected mutation assay undergo sweat testing for CF, and their families receive genetic counseling. The genetic counseling focuses on carrier risk for the parents of the newborn and offers carrier testing. We studied the yield of genetic counseling and the resulting genetic testing performed on the families of infants found to be CF carriers who underwent sweat testing in a single institution.

RESULTS

Of 102 newborns evaluated with a single CF mutation, 2 (twins) had sweat test results consistent with CF. A total of 101 families were counseled, and 95 were offered DNA-based CF carrier testing. Eighty-two percent of all parents chose to have CF carrier testing, and in five couples, both members were carriers. One of these couples (whose newborn was only a carrier) had an older child who was unexpectedly found to have CF.

CONCLUSIONS

Sweat testing of newborns at increased risk for CF in conjunction with genetic counseling for their parents allows identification of infants with CF, finds couples at high risk for having a child with CF, identifies previously undiagnosed siblings with CF, and allows for potential identification of CF carriers in the extended family.