While genetic testing can be helpful in identifying a familial link, there are several issues concerning the use of genetic tests for screening and diagnosis of polyposis syndromes that should be considered. First, no single test can be considered sufficient for diagnosis or for the development of a care plan for a child with GI polyps. This is due to the fact that most polyposis syndromes are associated with more than one gene mutation and, conversely, a gene may be associated with several different syndromes. Gene testing following genetic counseling is most appropriate when an affected relative is known to have tested positive. Then, an identical test can be used to screen individuals in the family for the inherited syndrome. Even when appropriately performed, genetic tests have wide-ranging implications, including both psychosocial aspects (such as the impact on life insurability and, less frequently, on health insurance) and the psychologic impact of both a positive and negative gene test. Testing of younger, clinically unaffected siblings may have profound psychological consequences that may not be justified if there is no impact on subsequent care. Generally, children are tested when they are older than 10 years. Continued surveillance and possible referral for genetic counseling is recommended for children with polyps clearly associated with a heightened risk of colorectal cancer.
Presymptomatic screening of potentially affected individuals has been shown to significantly affect the natural history of familial adenomatous polyposis and possibly that of the other polyposis syndromes. If a hereditable polyposis syndrome is identified, other family members should be alerted and screened.