MYTH: All genetic tests are based on DNA.
FACT: Genetic tests that analyze human DNA or RNA are known as direct testing. Other tests analyze chromosomes (cytogenetic testing), markers linked to genes (linkage analysis testing), or certain metabolites (biochemical testing) to detect gene changes related to an inherited condition. For more information about genetic testing, see the GeneTests Web site at http://www.genetests.org.
MYTH: Genetic testing can determine whether all of a person's genes are normal.
FACT: Current genetic testing looks for changes (mutations) in a specific gene, such as the gene mutation that causes cystic fibrosis. Current tests don't examine every single gene in a person.
MYTH: Genetic test results indicate whether an adult will develop a specific disease, such as breast cancer.
FACT: Genetic testing can indicate whether a person has a specific gene change or the normal copy of the gene. For some conditions such as Huntington's disease, identifying the gene change in a person confirms the diagnosis and indicates that the person will develop the disease. For other conditions, such as hereditary breast cancer, finding a gene mutation confirms increased susceptibility to the condition, but doesn't guarantee that the person will develop the disease.
MYTH: A genetic profile test can help a person take steps to prevent a myocardial infarction (MI).
FACT: At this point, genetic test profiling doesn't provide any information that changes what we already know about MI prevention or management. Warn patients that sequencing the human genome has heightened expectations that genetic tests can offer people individualized estimates of disease risk. A number of commercial companies are offering genetic tests that may not be clinically valid. Patients who have questions about tests should contact a local genetics professional; a directory is available on the GeneTests Web site. Quackwatch (http://www.quackwatch.org) also has information on inappropriate commercial genetic testing.
Dale Halsey Lea is assistant director of the Southern Maine Genetics Services at the Foundation for Blood Research in Scarborough, Me., and a past president and founder of the International Society of Nurses in Genetics. Selected references for this article are available on request.