The DNA analysis service for familial adenomatous polyposis was set up in 1996 and is one of the few in the UK offering a clinical diagnostic service which is undertaken by a certified NHS laboratory.

The gene responsible for FAP, known as the APC gene, is considered to be a large gene and is located on chromosome 5. The mutation varies from family to family and to date many hundred mutations have been identified.

Blood is taken from an affected individual, DNA is then extracted and the gene is screened for the mutation. Because the gene is a large one, comprising 15 exons searching for the mutation can be time consuming. There are several areas, known as hotspots, in which mutations occur most frequently. Others are more difficult to detect and in about 10% of cases the mutation cannot be identified using current methods.

Once the causative mutation has been identified in a family all those at risk can be offered diagnostic testing.

It is recommended that genetic counselling is offered and a consent form signed before proceeding with any form of DNA analysis.