Doctors uses the family history as the first stop in the assessment of genetic risks for any individual.
For many genetic disorders, there will be no obvious signs of symptoms until significant medical problems surface, so family history may be the only way to identify individuals at risk. This in turn can lead to a program of surveillance and management to mitigate the effects of the condition.
Although the gold standard is a three-generation pedigree, many patients will not have all of the relevant information at their fingertips at the time of a clinic visit, and eliciting a full pedigree can be time-consuming; nevertheless, a set of pointed questions can identify risk for some of the more common conditions for which genetic testing is available.
These include disorders that lead to an increased risk of cancer, sudden death due to cardiac dysfunction, hyperlipidemia, adverse drug reactions, and others. Recognition of the major patterns of genetic transmission, i.e., dominant and recessive, autosomal and sex-linked, can reveal individuals and family members at risk who may benefit from genetic testing.
Genetic testing itself is a process, beginning with recognizing the most appropriate test, explaining the risks, benefits, and limitations of testing to the patient, selecting an appropriate laboratory, and organizing testing with the laboratory.
In some cases, this may be done by a non-genetic specialist, whereas in others the complexity of ordering and interpreting tests warrants involvement of a genetics specialist.
In either case, the clinician and genetic counselors needs to be prepared to help interpret the results in light of the family history and clinical presentation and to support the patient in future management and decision-making.
Genetic test results may also have implications for other family members, which also need to be factored into pre- and post-test counseling.
The National Society of Genetic Counselors (NSGC) officially defines genetic counseling as the understanding and adaptation to the medical, psychological and familial implications of genetic contributions to disease. This process integrates:
- Interpretation of family and medical histories to assess the chance of disease occurrence or recurrence.
- Education about inheritance, testing, management, prevention, resources
- Counseling to promote informed choices and adaptation to the risk or condition.
A genetic counselor is an expert with a Master of Science degree in genetic counseling. In the United States they are certified by the American Board of Genetic Counseling. In Canada, genetic counselors are certified by the Canadian Association of Genetic Counsellors. Most enter the field from a variety of disciplines, including biology, genetics, nursing, psychology, public health and social work. Genetic counselors should be expert educators, skilled in translating the complex language of genomic medicine into terms that are easy to understand.
Genetic counselors work as members of a health care team and act as a patient advocate as well as a genetic resource to physicians. Genetic counselors provide information and support to families who have members with birth defects or genetic disorders, and to families who may be at risk for a variety of inherited conditions. They identify families at risk, investigate the problems present in the family, interpret information about the disorder, analyze inheritance patterns and risks of recurrence, and review available genetic testing options with the family.
Genetic counselors are present at high risk or specialty prenatal clinics that offer prenatal diagnosis, pediatric care centers, and adult genetic centers. Genetic counseling can occur before conception (i.e. when one or two of the parents are carriers of a certain trait) through to adulthood (for adult onset genetic conditions, such as Huntington’s disease or hereditary cancersyndromes).
Reasons for testing
Families or individuals may choose to attend counseling or undergo prenatal testing for a number of reasons.
- Family history of a genetic condition or chromosome abnormality
- Molecular test for single gene disorder
- Increased maternal age (35 years and older)
- Increased paternal age (40 years and older)
- Abnormal maternal serum screening results or ultrasound findings
- Increased nuchal translucency measurements on ultrasound
- Strong family history of cancer
- Predictive testing for adult-onset conditions
Many disorders cannot occur unless both the mother and father pass on their genes, such as Cystic Fibrosis. Some diseases can be inherited from one parent, such as Huntington disease, and DiGeorge syndrome. Other genetic disorders are the cause of an error or mutation occurring during the cell division process (e.g.trisomy). Testing can reveal conditions that are easily treatable as long as they are detected (Phenylketonuria or PKU). Genetic tests are available for a number of genetic conditions including but not limited to:
Patients may be referred to a genetic counselor based on their cancer diagnosis, or a strong family history of cancer. It is estimated that only 5-10% of cancers are hereditary, meaning that these cancers are due to a gene mutation that has been passed down in the family. Some examples of known cancer syndromes are hereditary breast and ovarian cancer syndrome, hereditary non-polyposis colorectal cancer and Li-Fraumeni syndrome. Meeting with a genetic counselor before undergoing genetic testing will help an individual to understand the test and what the results may mean for themselves and their family. Once the results are received, genetic counselors can help the patient to understand a positive or negative result. This counseling may involve providing emotional support, discussing recommendations for preventative care, screening recommendations or referrals to support groups or other resources. For patients who have already been diagnosed with cancer, a positive test result may influence how the cancer is treated.
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