genetic counseling

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Definition

Genetic counseling aims to facilitate the exchange of information regarding a person's genetic legacy. It attempts to:

• accurately diagnose a disorder
• assess the risk of recurrence in the concerned family members and their relatives
• provide alternatives for decision-making
• provide support groups that will help family members cope with the recurrence of a disorder

Description

With approximately 2,000 genes identified and approximately 5,000 disorders caused by genetic defects, genetic counseling is important in the medical discipline of obstetrics. Genetic counselors, educated in the medical and the psychosocial aspects of genetic diseases, convey complex information to help people make life decisions. There are limitations to the power of genetic counseling, though, since many of the diseases that have been shown to have a genetic basis currently offer no cure (for example, Down syndrome or Huntington's disease). Although a genetic counselor cannot predict the future unequivocally, he or she can discuss the occurrence of a disease in terms of probability.

A genetic counselor, with the aid of the patient or family, creates a detailed family pedigree that includes the incidence of disease in first-degree (parents, siblings, and children) and second-degree (aunts, uncles, and grandparents) relatives. Before or after this pedigree is completed, certain genetic tests are performed using DNA analysis, x ray, ultrasound, urine analysis, skin biopsy, and physical evaluation. For a pregnant woman, prenatal diagnosis can be made using amniocentesis or chorionic villus sampling.

An important aspect of the genetic counseling session is the compilation of a family pedigree or medical history. To accurately assess the risk of inherited diseases, information on three generations, including health status and/or cause of death, is usually needed. If the family history is complicated information from more distant relatives may be helpful, and medical records may be requested for any family members who have had a genetic disorder. Through an examination of the family history a counselor may be able to discuss the probability of future occurrence of genetic disorders. In all cases, the counselor provides information in a non-directive way that leaves the decision-making up to the client.

Screening blood tests help identify individuals who carry genes for recessive genetic disorders. Screening tests are usually only done if:

• The disease is lethal or causes severe handicaps or disabilities
• The person is likely to be a carrier due to family pedigree or membership in an at-risk ethnic, geographic or racial group
• The disorder can be treated or reproductive options exist
• A reliable test is available.

Genetic disorders such as Tay-Sachs disease, sickle-cell anemia, and thalassemia meet these criteria, and screening tests are commonly done to identify carriers of these diseases. In addition, screening tests may be done for individuals with family histories of Huntington's disease (a degenerative neurological disease) or hemophilia (a bleeding disorder). Such screening tests can eliminate the need for more invasive tests during a pregnancy.

Another screening test commonly used in the United States in the alpha-fetoprotein (AFP) test. This test is done on a sample of maternal blood around week 16 of a pregnancy. An elevation in the serum AFP level indicates that the fetus may have certain birth defects such as neural tube defects (including spina bifida and anencephaly). If the test yields an elevated result, it may be run again after seven days. If the level is still elevated after repeat testing, additional diagnostic tests (e.g. ultrasound and/or amniocentesis) are done in an attempt to identify the specific birth defect present.

Ultrasound is a noninvasive procedure which uses sound waves to produce a reflected image of the fetus upon a screen. It is used to determine the age and position of the fetus, and the location of the placenta. Ultra-sound is also useful in detecting visible birth defects such as spina bifida (a defect in the development of the vertebrae of the spinal column and/or the spinal cord). It is also useful for detecting heart defects, and malformations of the head, face, body, and limbs. This procedure, however, cannot detect biochemical or chromosomal alterations in the fetus.

Amniocentesis is useful in determining genetic and developmental disorders not detectable by ultrasound. This procedure involves the insertion of a needle through the abdomen and into the uterus of a pregnant woman. A sample of amniotic fluid is withdrawn containing skin cells that have been shed by the fetus. The sample is sent to a laboratory where fetal cells contained in the fluid are isolated and grown in order to provide enough genetic material for testing. This takes about seven to 14 days. The material is then extracted and treated so that visual examination for defects can be made. For some disorders, like Tay-Sachs disease, the simple presence of a telltale chemical compound in the amniotic fluid is enough to confirm a diagnosis.

Chorionic villus sampling involves the removal of a small amount of tissue directly from the chorionic villi (minute vascular projections of the fetal chorion that combine with maternal uterine tissue to form the placenta). In the laboratory, the chromosomes of the fetal cells are analyzed for number and type. Extra chromosomes, such as are present in Down syndrome, can be identified. Additional laboratory tests can be performed to look for specific disorders and the results are usually available within a week after the sample is taken. The primary benefit of this procedure is that it is usually performed between weeks 10 and 12 of a pregnancy, allowing earlier detection of fetal disorders.

— Jeffrey P. Larson, RPT

The counseling of individuals, and of prospective parents regarding their offspring, on the probabilities, dangers, diagnosis, and treatment of inherited diseases.

The process of advising a patient with a genetic disease, or child-bearing parents of a patient with a genetic disease, about the probabilities and risks of future genetic accidents in conception, and counseling such persons about future family planning.

Over the last half-century, our understanding of genetic disorders has increased spectacularly. When facts about inherited disorders first came to light, health professionals began to inform families about probable inheritance patterns and recurrence risks (the likelihood that offspring or other relatives might also inherit the disease).

The Need for Genetic Counseling

Receiving a diagnosis of a genetic disorder can have profound impact for both patients and their family members, and it quickly became clear that aside from the need for medical and genetic information, families affected by genetic disorders had educational, social, and psychological needs that required attention. And though families were afflicted with different disorders passed on by different modes of inheritance (autosomal recessive, autosomal dominant, complex, or some other type), certain reactions were observed again and again.

For instance, some parents of children with an autosomal recessive disorder felt profound guilt at having transmitted an inherited disorder to their child. On the other hand, a family member who was spared a genetic disorder that other family members developed frequently suffered "survivor guilt." Health-care providers also noted that family members at risk for developing a late-onset disorder live with intense anxiety about the future and often needed support and counseling. Finally, counseling was seen to be of potential help for family members who incorrectly inferred that they were at risk for having a child with a genetic disorder. Attempts to meet these varied needs and help give people a sense of control over their situation resulted in the emergence of a model of genetic education and support that came to be called genetic counseling.

An Evolving Field

In time, genetic counseling evolved into a profession. Since the early 1970s genetic counselors have been members of health-care teams providing comprehensive and consistent medical genetic services, while also tending to the social and emotional welfare of the patients and their families. In the United States, the first master's degree training program for genetic counseling was established in 1971. Since then the profession has grown tremendously. There are now more than 2,500 genetic counselors in the United States and 25 genetic counseling training programs. Many industrialized countries have adopted the United States's model of training for genetic counselors, and master's-level training programs now exist in Canada, Australia, Great Britain, and South Africa.

As the profession grows, the definition of genetic counseling also continues to evolve. Genetic counseling is currently defined as "a communication process, which helps an individual and/or family in a variety of ways." For instance, genetic counselors help patients and their families to comprehend the medical facts, including the diagnosis, probable course of the disorder, and available treatment options. Genetic counselors also help educate their clients about the way heredity contributes to the disorder and the risk of recurrence in relatives, and to understand the options available for dealing with this risk of recurrence.

Genetic counselors also teach their clients the medical facts relating to a disorder, enabling them to make informed, independent decisions. They understand that only if their clients possess the necessary facts about available medical care and genetic testing can their decisions be free of coercion. Finally, genetic counselors provide information helpful in accessing local and national support resources.

A key aspect of the genetic counselor's work is educational: helping clients to comprehend the genetic implications of their disorder. In addition, the diagnosis of a genetic disorder in an individual often leads to identification of other family members who may be at risk for having or passing on a genetic disorder, so genetic counselors often work with entire families. For instance, if the genetic tests of a female patient with two sisters disclose that she has a genetic change (mutation) in the BRCA1 gene, then her two sisters are at risk for carrying this same genetic change, which can cause breast cancer. Once the patient has been notified and has given her permission, these sisters would then be contacted and given the chance to learn about their own risk of carrying a disease-causing gene.

This second round of counseling is important. Armed with the information about their susceptibility for breast cancer, the sisters might choose to undergo genetic testing themselves, or they might begin early detection screening evaluations. Their new knowledge might also lead them to adopt lifestyle changes that could reduce their risk of developing breast cancer. Even when genetic testing is not available, early identification of at-risk patients and their family members can be valuable and quite possibly lifesaving.

The demand for genetic education and counseling will likely increase as knowledge accumulates about the genetic component of commonly occurring disorders such as breast cancer, Alzheimer's disease, heart disease, diabetes mellitus, and osteoporosis. As a result, a variety of professional specialists, such as genetic educators, physicians, nurses, social workers, medical geneticists, and genetic counselors, will increasingly be called upon to provide genetic education and counseling. Of this group, however, genetic counselors and medical geneticists are the most qualified to perform comprehensive genetic counseling.

Protection As Well As Education

At the same time that they provide beneficial genetic counseling to patients and their families, professionals providing such a service must have a full understanding of the dangers of eugenics. The abuse of genetic information has led to many atrocities in the past. In Germany, the Nazis murdered nearly 7 million "genetically defective" people during World War II and forcibly sterilized nearly half a million others, all in the name of "eugenics"—a policy that calls for the systematic elimination of "unfit" members of the population. The United States also has a checkered past with respect to eugenics. In the early twentieth century, the United States passed laws allowing sterilization of the mentally handicapped and limiting the number of "genetically inferior" ethnic groups that were allowed to immigrate.

In order to prevent such abuses from ever occurring again, the genetic counseling profession has followed in the footsteps of other health-care professions by establishing a code of ethics guiding professional behavior. Policies such as nondirectiveness, prevention of genetic discrimination, respect for patients' beliefs, complete disclosure, and informed consent are components of these ethical principles. Nondirectiveness, one of the major tenets of genetic counseling, is defined by the National Society of Genetic Counselors as enabling "clients to make informed independent decisions, free of coercion, by providing or illuminating the necessary facts and clarifying the alternatives and anticipated consequences."

Genetic counseling has become a vital part of medical genetics. With the knowledge gained from the past and the tools to help patients choose their paths, genetic counseling will continue to be invaluable in the rapidly growing field of human genetics.

Bibliography

Epstein C. J., et al. "Genetic Counseling." American Journal of Human Genetics 27 (1975): 240-242.

Fine, B., and M. Koblenz. "Conducting Pre-Test Patient Education." In Humanizing Genetic Testing: Clinical Applications of New DNA Technologies. Evanston, IL: Northwestern University, 1994.

Kessler, S. "Psychological Aspects of Genetic Counseling VI: A Critical Review of the Literature Dealing with Education and Reproduction." American Journal of Medical Genetics 34 (1989): 340-353.

———. "Process Issues in Genetic Counselling." Birth Defects 28, no. 1 (1992): 1-10.

National Society of Genetic Counselors. "Genetic Counseling as a Profession." In National Society of Genetic Counselors. Wallingford, PA: National Society of Genetic Counselors, Inc., 1983.

Reed, S. "A Short History of Genetic Counseling." Social Biology 21 (1974): 332-339.

—Chantelle Wolpert

The practice of counseling a person about the results of genetic testing so that the results are accurately understood. The person being counseled may then make a more informed decision about any actions to be taken.

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