Chapter 064. The Practice of Genetics in Clinical Medicine (Part 6)

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Follow-Up Care after Testing Depending on the nature of the genetic disorder, posttest interventions may include (1) cautious surveillance and appropriate health care screening, (2) specific medical interventions, (3) chemoprevention, (4) risk avoidance, and (5) referral to support services. For example, patients with known pathologic mutations in BRCA1 or BRCA2 are offered intensive screening as well as the option of prophylactic mastectomy and oophorectomy. In addition, such women may be eligible for preventive treatment with tamoxifen, or enrollment in a chemoprevention clinical trial. In contrast, those at known risk for Huntington's disease are offered continued follow-up and supportive services,...

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Chapter 064. The Practice of Genetics in Clinical Medicine (Part 6) Follow-Up Care after Testing Depending on the nature of the genetic disorder, posttest interventions may include (1) cautious surveillance and appropriate health care screening, (2) specific medical interventions, (3) chemoprevention, (4) risk avoidance, and (5) referral to support services. For example, patients with known pathologic mutations in BRCA1 or BRCA2 are offered intensive screening as well as the option of prophylactic mastectomy and oophorectomy. In addition, such women may be eligible for preventive treatment with tamoxifen, or enrollment in a chemoprevention clinical trial. In contrast, those at known risk for Huntington's disease are offered continued follow-up and supportive services, including physical and occupational therapy, and social services or support groups, as indicated. Specific interventions will change as translational research continues to
enhance our understanding of these genetic diseases and as more is learned about the functions of the gene products involved. Individuals who test negative for a mutation in a disease-associated gene identified in an affected family member must be reminded that they may still be at risk for the disease. This is of particular importance for common diseases such as diabetes mellitus, cancer, and coronary artery disease. For example, a woman who finds that she does not carry the disease-associated mutation in BRCA2 previously discovered in her family must be reminded that she still requires the same breast cancer screening recommended for the general population.[newpage] Genetic Counseling and Education Genetic counseling should be distinguished from genetic testing and screening, even though genetic counselors are often involved in issues related to testing. Genetic counseling refers to a communication process that deals with human problems associated with the occurrence or risk of a genetic disorder in a family. Genetic risk assessment is complex and often involves elements of uncertainty. Counseling therefore includes genetic education as well as psychosocial counseling. Genetic counselors may be called upon by other health care professionals (or by individual patients and families) to address a broad range of issues directly and indirectly related to genetic disease (Table 64-1). The role of the genetic counselor includes the following:
Gather and document a detailed family history; Educate patients about general genetic principles related to disease risk, both for themselves and for others in their family; Assess and enhance the patient's ability to cope with the genetic information offered; Discuss how nongenetic factors may relate to the ultimate expression of disease; Address medical management issues; Assist in determining the role of genetic testing for the individual and family; Ensure that the patient is aware of the indications, process, risks, benefits, and limitations of the various genetic testing options; Assist the patient, family, and referring physician in the interpretation of the test results; and Refer the patient and other at-risk family members for additional medical and support services, if necessary. Table 64-1 Indications for Genetic Counseling
Advanced maternal (>35) or paternal (>50) age Consanguinity Previous history of a child with birth defects or a genetic disorder Personal or family history suggestive of a genetic disorder High-risk ethnic groups; known carriers of genetic alterations Documented genetic alteration in a family member Ultrasound or prenatal testing suggesting a genetic disorder The complexity of genetic counseling and the broad scope of genetic diseases have led to the development of specialized, multidisciplinary clinics designed to provide broad-based support and medical care for those at risk and their family members. Such specialty clinics are well established in the areas of cancer and neurodegenerative disorders. The multidisciplinary teams are often composed of medical geneticists, specialist physicians, genetic counselors, nurses, psychologists, social workers, and biomedical ethicists who work together to consider difficult diagnostic, treatment, and testing decisions. Such a format also provides primary care physicians with invaluable support and assistance as they follow and treat at-risk patients.
The approach to genetic counseling has important ethical, social, and financial implications. Philosophies related to genetic counseling vary widely by country and center. In North American centers, for example, counseling is generally offered in a nondirective manner, wherein patients learn to understand how their values factor into a particular medical decision. Nondirective counseling is particularly appropriate when there are no data demonstrating a clear benefit associated with a particular intervention or when an intervention is considered experimental. For example, nondirective genetic counseling is employed when a person is deciding whether to undergo genetic testing for Huntington's disease (Chap. 365). At this time, there is no clear benefit (in terms of medical outcome) to an at-risk individual undergoing genetic testing for this disease, as its course cannot be altered by therapeutic interventions. However, testing can have an important impact on this individual's perception of the future and his or her interpersonal relationships and plans for reproduction. Therefore, the decision to pursue testing rests on the individual's belief system and values. On the other hand, a more directive approach is appropriate when a condition can be treated. In a family with FAP, colon cancer screening and prophylactic colectomy should be recommended for known APC mutation carriers. The counselor and clinician following this family must ensure that the at-risk family members have access to the resources necessary to adhere to these recommendations.
Genetic education is central to an individual's ability to make an informed decision regarding testing options and treatment. Although genetic counselors represent one source of genetic education, other health care providers also need to contribute to patient education. Patients at risk for genetic disease should understand fundamental medical genetic principles and terminology relevant to their situation. This includes the concept of genes, how they are transmitted, and how they confer hereditary disease risk. An adequate knowledge of patterns of inheritance will allow patients to understand the probability of disease risk for themselves and other family members. It is also important to impart the concepts of disease penetrance and expression. For most complex adult-onset genetic disorders, asymptomatic patients should be advised that a positive test result does not always translate into future disease development. In addition, the role of nongenetic factors, such as environmental exposures, must be discussed in the context of multifactorial disease risk and disease prevention. Finally, patients should understand the natural history of the disease as well as the potential options for intervention, including screening, prevention, and—in certain circumstances— pharmacologic treatment or prophylactic surgery.