"Code of practice and guidance on human genetic testing services supplied direct to the public". Advisory Committee on Genetic Testing

Are the kids really all right? Direct-to-consumer genetic testing in children: are company policies clashing with professional norms?

The genetic testing of minors within the direct-to-consumer (DTC) genetic testing (GT) context has been given relatively little attention. The issue of testing healthy children for diseases that would only develop in adulthood raises many important ethical, legal and social issues. As genetic testing is now available outside of the traditional health care system, often without even the intermediate of a health care professional, we surveyed 37 DTC GT companies regarding their policies for testing in children. Although the response rate is relatively low (35%, 13/37), our findings reveal that a clear majority of companies do perform genetic testing in minors. As such, companies testing for adult onset diseases are acting in contradiction of established professional guidelines, which state, among others, that, for predictive genetic testing, the availability of therapeutic or preventive measures is necessary for testing to be performed in asymptomatic minors. The community of stakeholders in children's health care and genetic testing should, therefore, decide which standards need to be upheld by DTC GT companies and ensure that these are met.

Improving the prediction of complex diseases by testing for multiple disease-susceptibility genes

Studies have argued that genetic testing will provide limited information for predicting the probability of common diseases, because of the incomplete penetrance of genotypes and the low magnitude of associated risks for the general population. Such studies, however, have usually examined the effect of one gene at time. We argue that disease prediction for common multifactorial diseases is greatly improved by considering multiple predisposing genetic and environmental factors concurrently, provided that the model correctly reflects the underlying disease etiology. We show how likelihood ratios can be used to combine information from several genetic tests to compute the probability of developing a multifactorial disease. To show how concurrent use of multiple genetic tests improves the prediction of a multifactorial disease, we compute likelihood ratios by logistic regression with simulated case-control data for a hypothetical disease influenced by multiple genetic and environmental risk factors. As a practical example, we also apply this approach to venous thrombosis, a multifactorial disease influenced by multiple genetic and nongenetic risk factors. Under reasonable conditions, the concurrent use of multiple genetic tests markedly improves prediction of disease. For example, the concurrent use of a panel of three genetic tests (factor V Leiden, prothrombin variant G20210A, and protein C deficiency) increases the positive predictive value of testing for venous thrombosis at least eightfold. Multiplex genetic testing has the potential to improve the clinical validity of predictive testing for common multifactorial diseases.

Motivations and concerns of patients with access to genetic testing for hereditary pancreatitis

OBJECTIVES

Direct DNA testing is now available for hereditary pancreatitis (HP). This study aimed to identify the factors that motivated individuals to participate in research and to determine how research participants used their genetic test results.

METHODS

A survey was mailed to 247 participants (110 male, 137 female) who were > or =18 yr of age and living in the US. Data analysis was primarily a description of frequency distribution of the responses.

RESULTS

Ninety-one of 247 participants (37%) completed the survey. Of the 55 female and 36 male respondents, 60% were 31-55 yr old, and a total of 54% tested positive for HP. The most common reason for participating in research was "to help a relative/family member" (61%), and genetic testing was pursued because of "the disturbance of seeing affected relatives" (48%) and "the desire to help future generations" (33%). Perceived risk of developing HP in the future was the least important motivating factor in seeking genetic testing. Sixty-two percent of respondents had received their genetic test results. All but one chose to share their results with at least one person: most often with family members (96%) and physicians (62%), and least often with insurance companies (4%). The most common influential factor in withholding information was "the fear of insurance discrimination" (23%).

CONCLUSIONS

The major motivations to participate in the HP genetic research study were to obtain genetic testing and to help current family members and future generations. The major concern was insurance discrimination. Participants clearly appreciate the availability of genetic testing for HP. These results suggest that a mechanism to disclose results to research participants should be considered, and effective ways to protect at-risk individuals from insurance discrimination must remain a genetics health care priority.

Genetic testing. Counseling, laboratory, and regulatory issues and the EUROPAC protocol for ethical research in multicenter studies of inherited pancreatic diseases

This article highlights several of the important issues and illustrates a European protocol that should be considered when offering genetic testing on a research or clinical basis for HP, as well as for other inherited disorders of the pancreas.

On the use of population-based registries in the clinical validation of genetic tests for disease susceptibility

PURPOSE

Many new genetic tests for susceptibility to adult-onset diseases are developed on the basis of selected and high-risk groups. Before such tests can be used in medical practice, however, epidemiologic studies must be conducted to evaluate their clinical sensitivity, specificity, and positive predictive value in the general population. For many common adult-onset diseases, this process may take decades of follow-up.

METHOD

We illustrate how clinical validation of new predictive genetic tests can be done retrospectively using case-control studies that are derived from population-based registries of diseases. We use the examples of birth defects and cancer registries to illustrate a hypothetical process by which such tests can be clinically validated.

RESULTS

We demonstrate how such epidemiologic studies can be successfully used to derive measures of a test's sensitivity, specificity, positive predictive value, negative predictive value, and of the population attributable fraction of disease due to the disease-susceptibility genes. Under certain assumptions, data derived from population-based case-control studies provide adequate estimates of lifetime risks for disease (penetrance) among people with specified genotypes.

CONCLUSIONS

With adequate protections of human subjects, studies involving population-based registries of disease will increasingly become valuable in validating the numerous genetic tests that will emerge from advances in human genetic research and the Human Genome Project.