Information About Genetic Testing
Genetic testing involves looking at a person’s genetic information in order to detect mutations that have either been inherited from a parent (for example, changes that may result in a heritable disease) or acquired during the person’s lifetime (like those that could lead to the development of cancer). Genetic testing may involve an analysis of specific genes (segments of DNA that provide the instructions for a specific protein), chromosomes (the packages of a person’s DNA within the body’s cells), or proteins ( the products of our genes). Most gene tests involve looking for changes in the DNA sequence. That is, they look at the order of the adenines (A), thymines (T), guanines (G), and cytosines (C) that combine to make DNA, which is then packaged in the chromosomes (See Figure 1). Changes in DNA sequence could lead to a non-functional gene or a gene that functions improperly.
There are many different types of genetic testing, including:
- Diagnostic testing
- When the results can help establish or rule out a specific diagnosis in a person exhibiting symptoms of a genetic condition
- Predictive or pre-symptomatic testing
- When the results are used to predict disease in a person currently showing no signs of the disorder in question
- Susceptibility testing
- When the results are used to determine whether a healthy individual is more likely to develop a specific disease
- Carrier testing
- When the results are used to identify individuals who may be at risk to have a child with a recessive disorder
- Prenatal diagnosis
- When the testing is performed during pregnancy using a sample containing the baby’s DNA
- Pharmacogenetic testing
- When the results may help determine how a person will respond to a treatment with a specific medication
Genetic testing differs from other types of medical tests in several important ways. First, genetic testing may provide information about future disease in a healthy individual (such as the development of Alzheimer’s disease). In addition, genetic test results may influence reproductive decision-making, family planning, and other major life decisions. Furthermore, the results may provide information about family members and could also reveal unexpected findings (such as non-paternity).
Because of the nature of genetic testing, including the significant impact it may have on an individual and his/her family, it is generally recommended that anyone considering genetic testing undergo genetic counseling. Genetic counseling helps the individual or family understand relevant medical facts and inheritance patterns. In addition, it is critical for reviewing the risks, benefits, and limitations of the genetic test(s) being considered, and it offers patients the opportunity to learn about the implications of the possible test results. Finally, genetic counseling allows individuals to choose a course of action in accordance with their beliefs and values and helps them adjust to the information provided.
Genetic counseling services are provided by specially trained healthcare providers who have significant experience with genetics and the unique nature of genetic testing. Genetic counselors are healthcare providers with graduate degrees from programs accredited by the American Board of Genetic Counselors (ABGC). They have received training in both medical genetics and psychology. A local, board-certified genetic counselor may be found through the National Society of Genetic Counselors.
Genetic Testing for Alzheimer’s Disease
In 2011, the American College of Medical Genetics (ACMG) and the National Society of Genetic Counselors (NSGC) published guidelines regarding genetic testing for Alzheimer’s disease (AD). In these guidelines, the ACMG and NSGC state that APP, PSEN1, or PSEN2 gene testing may be considered in individuals with a personal and family history consistent with early-onset AD inherited in a dominant manner. However, they recommend that genetic testing not be performed without appropriate genetic counseling and informed consent. For individuals with a personal or family history consistent with late-onset AD, APOE gene testing is possible but not currently recommended. In addition, genetic testing for AD (APP, PSEN1, PSEN2, or APOE) should not be performed in any individual under the age of 18.
Genetic testing for AD, which is available on a clinical basis, must be ordered by a physician. However, at the present time, most major insurers consider this testing experimental or investigational. Consequently, APP, PSEN1, PSEN2, and APOE gene tests are unlikely to be covered by many insurance plans.
Because of the rapid advances in medical genetics, we now have a better understanding of how mutations in our DNA can affect our health and our risk for most diseases. We have learned that differences in a person’s DNA may determine a person’s chance of having a genetic syndrome, developing cancer, or developing other common adult-onset disorders, such as diabetes, heart disease, and Alzheimer’s disease. They may also help determine how a person may respond to a specific treatment or medication. In general, genetic testing has become a valuable tool in the diagnosis of genetic disorders, the prediction of future disease, and the management of those who are affected or at risk for a condition with a genetic basis. However, many people have concerns regarding how their genetic information may be used. Because of such concerns, and because of a history of cases documenting genetic discrimination, a law to address this issue was passed in 2008.
The Genetic Information Nondiscrimination Act (GINA), which took effect in 2009, helps protect citizens from genetic discrimination. According to this law, genetic information includes both genetic testing results and family history (for example, a known genetic condition in a relative or a family member known to carry a disease-related gene change). The first part of GINA (Title I), which applies to insurers offering healthcare coverage, prevents insurers from using an individual’s genetic information to determine eligibility or coverage or to set member premiums. It also prohibits insurers from considering family history or genetic test results as pre-existing conditions, and states that an insurer may not require genetic testing in any plan member. The second part of GINA (Title II) prevents employers from using a person’s genetic information for employment-related decisions, including decisions to hire, promote, or terminate an employee. In addition, employers may not require genetic testing and may not request genetic information from their employees.
GINA does not cover genetic conditions that have already been diagnosed based on the presence of disease symptoms. In addition, GINA does not cover other types of insurance, such as life insurance, disability insurance, or long-term care insurance.