LabPLUS is part of Auckland District Health Board
and provides medical laboratory testing
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MOLECULAR GENETICS TESTS - FAMILIAL ADENOMATOUS POLYPOSIS |
| Background: Familial adenomatous polyposis (FAP) is an autosomal dominant condition affecting nearly 1 in 5000 people. It is characterised by the progressive development of hundreds to thousands of adenomatous colon polyps, some of which inevitably progress to carcinoma if the colon is not surgically removed. Age of onset of polyp development can be as early as 11 or 12, and malignant transformation can occur as late as the 7th decade. As classically defined, FAP has no associated extracolonic manifestations. However, there is at least one syndrome complex that is allelic to FAP: Gardner syndrome. Features of Gardner syndrome include colonic polyposis, polyps of the stomach and small intestine, globoid osteoma especially of the mandible and calvarium, congenital hypertrophy of the retinal pigment epithelium, epidermoid cysts and desmoid tumours. Rarely, adrenal carcinoma, thyroid carcinoma, periampullary carcinoma and hepatoblastoma (especially in children under age 4) can be seen in patients with FAP/Gardner. A second condition, Turcot syndrome, may be related to FAP. It is characterised by colonic polyposis and brain tumours (gliomas). The disease frequency for this documented condition is 1 in 5000 and an estimated 2 in 5000 individuals are at 50% risk for the disorder. Thus, there are more than 50,000 people in the United States alone who would benefit from genetic counselling, cancer surveillance and molecular genetic studies. Cancer surveillance for at risk individuals includes annual colonoscopy and upper gastrointestinal endoscopy, annual examination of the skin and annual comprehensive physical including palpation of the thyroid. Molecular genetic studies can be useful in some families to refine risk estimates. With the identification and characterisation of the FAP gene (referred to as APC) on chromosome 5, it is now possible to determine the carrier status of individuals at risk by virtue of their family history by employing linkage analysis. A majority of families are informative if appropriate family members are available for study. Analysis:
Blood: 3 x 4.0mL whole blood into EDTA tubes . Invert several times to mix. Forward within 24-48 hours at ambient temperature. Paediatric Samples: Minimum of 3mL whole blood in EDTA tubes. Prenatal Samples:
Paraffin blocks of tissue are also acceptable. The tissue sample should not have had prolonged immersion in formalin before embedding. NOTE:
6 weeks once sample is received. Cost of test: FAP - $461.03 Note: Prices excludes GST (12.5%) and may change without notice. Please click on a link below to view information about another specific test.
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