Genetic Testing Offers Information and Dilemmas

Through a variety of laboratory techniques, typically involving a blood sample, genetic tests may determine if a person has a genetic condition or disease or is likely to develop it., individuals may wish to be tested if there is a family history of one specific disease; they show symptoms of a genetic disorder; or they are concerned about passing on a genetic problem to their children.

There are four basic types of genetic testing:

1. Carrier Identification includes genetic tests used by couples to determine if they carry a particular gene that can be passed to their children.
2. Prenatal Diagnosis is genetic testing of a fetus, typically to identify genes associated with mental retardation or physical deterioration.
3. Newborn Screening is frequently done as a preventative health measure to take advantage of treatment options currently available.
4. Late-onset Disorders screening is for adult diseases such as cancer and heart disease.

Many medical centers, including The Medical College of Wisconsin and its affiliates, Froedtert Hospital and Children's Hospital of Wisconsin, coordinate genetic testing for a variety of conditions. Genetic testing can help diagnose diseases, prescribe treatment and develop prognoses. These institutions perform genetic tests for conditions such as cystic fibrosis, muscular dystrophy, metabolic disorders, cancer, hemophilia, neurofibromatosis (characterized by unusual birthmarks and tumors), cleft palate syndrome and sickle cell anemia.

According to Christine Sauer, MS, CGC, a genetic counselor based at Children's Hospital, genetic testing can help make a diagnosis that would help families understand what's going on with a child. Additionally, if the diagnosis is already determined, genetic counseling helps the family know what to expect in the future or with other children. Unfortunately, genetic testing is not always able to provide a diagnosis for the family.

Genetic testing for metabolic disorders can make a big difference in a patient's life. Following diagnosis, diet and medication can be prescribed to avoid illness, and in some conditions, even prevent severe retardation and death.

Genetic Tests for Cancer
Currently, genetic tests are available on a fee-for-service basis for colon cancer, breast cancer and a cancer syndrome that involves endocrine glands, such as the thyroid. A test for breast cancer genes coordinated through the Froedtert & Medical College Cancer Genetics Screening Program, for example, costs about $2,600, which is often covered by insurance. There are also research studies available to identify gene mutations that may cause skin cancer (melanoma), prostate cancer, colon cancer and breast cancer. Research studies are generally free to participating patients.

Genetic counselors, like Dawn Allain, MS, CGC, help patients understand their risk of inheriting a cancer susceptibility gene. A complete family history is the first step in identifying cancer risk and determining if a patient is an appropriate candidate for genetic testing. Allain notes that sometimes a patient's perception of risk is much higher than it actually is.

Counselors and geneticists look for clues of genetic links to cancer, such as cancer at an early age, rare cancers (e.g., male breast cancer), multiple generations of individuals with cancer, or a family member with multiple cancers, such as breast cancer in both breasts, or colon and endometrial cancer in the same person.

"Deciding whether or not to be tested is a dilemma for many people," Allain says. "The question is whether they would do anything different if they knew for sure they had a mutated cancer gene versus just knowing that they are at high risk of developing cancer. Knowledge can be powerful, but testing isn't for everyone."

Patients who decide to have genetic testing performed may feel they have more control over their future and can pursue the most aggressive treatment, if necessary. They can also educate family members about risks of developing a disease. But a normal, or negative, test result only means the patient has the same risk of developing cancer as the general population; it doesn't rule out other causes of cancer. Only 5-10% of all cancers are hereditary.

Issues Related to Testing
As outlined in the web pages of the ELSI Project, (Ethical Legal and Social Implications in Science) There are a number of serious legal, social and ethical issues related to genetic testing, particularly of people who show no symptoms of a disease. For example, should testing be done before birth, at birth, as a child or in adulthood? What about the possibility that genetic information will be used for discrimination in employment or insurance coverage? Three main issues are the individual's right to privacy, obtaining informed consent from the individual before testing, and providing confidentiality by limiting access to genetic information.

For individuals, it is sometimes a difficult decision to undergo genetic testing. For instance, genetic testing can determine, long before symptoms are present, if an individual is likely to develop Huntington's disease. This condition doesn't usually present symptoms until the late 30s; death follows 10 or 15 years later, preceded by progressive loss of motor function and dementia. People with Huntington's have a 50% chance of passing on the gene to each of their children. But there is no cure. How will such a diagnosis from genetic testing affect the individual's life choices and his or her family and relationships? Whether it's estate planning or deciding not to get married, individuals who know they are at high risk for developing Huntington's disease may choose to live their lives differently. Most choose not to be tested.

The National Institutes of Health also highlights these issues:

• No effective interventions are yet available to improve the outcome of most inherited diseases.
• Negative (normal) test results might not rule out future occurrence of disease.
• Positive test results might not mean the disease will inevitably develop.

Testing positive for a genetic mutation can have a psychological impact on patients and their families. Genetic counselors spend a great deal of time discussing how family dynamics can be altered by the results of a genetic test. Some family members don't want to know the results. Patients may feel guilt for carrying a gene mutation and possibly passing it to their children. Some patients even feel guilt when they test negative in a family where a disease is prevalent.

"Our technology and knowledge is still limited," Allain says. "We can identify some, but not necessarily all, genes identified with a particular disease. But when we identify a gene mutation, it may provide a patient or family with an opportunity to make informed choices about medical management and life decisions. In the case of cancer, additional screening and close surveillance may lead to early detection of disease, and could save lives."

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.