Glossary
If there are any
other terms that you think would be worth adding to those below please let me know and I will add them to the list!
Barium enema –
An X-ray examination of the large bowel that is commonly used to find polyps and cancers. People who have had a positive FOB
test may be asked to have a barium enema.
Cancer – A
malignant tumour, that is, a tumour that has the capacity to spread locally and also to distant tissues and organs. A cancer
treated before it has spread widely is less likely to be fatal.
Colonoscopy –
An examination of the lower (large) bowel using a flexible scope. Polyps can be removed during the procedure and small tissue
samples (biopsies) taken from any areas that appear to be malignant eg an ulcer or large polyp. People who have had a positive
FOB test may be asked to have a colonoscopy.
Faeces – Sometimes
referred to as ‘stool’.
Haemoglobin –
The component of blood that carries oxygen and the part of blood that is detected by FOB testing.
Haemorrhoids –
Dilated veins around the anus that can bleed and result in a falsely positive FOB screening test.
Hereditary –
Conditions that run in families due to passing on of a genetic abnormality are called hereditary. This includes conditions
that increase the risk of colon cancer eg. Familial adenomatous polyposis coli.
Inflammatory bowel
disease – Conditions of the bowel (intestines) that cause abdominal pain and diarrhoea. The bowel lining is frequently
ulcerated and bleeds. People with inflammatory bowel disease have a slightly increased risk of developing colon cancer. The
two commonest types of inflammatory bowel disease are ulcerative colitis and Crohn’s disease. Screening for colon cancer
should start at a younger age in people with inflammatory bowel disease.
Monoclonal antibody
– A molecule that will attach specifically to another molecule. The monoclonal antibody used in the Actim FOB test will
bind to a specific part of the human globin molecule in human haemogloblin.
Polyp – A
localised tumour that can have a narrow stalk or a wide base. Some polyps can develop into cancers over a period of years.
Removing polyps can prevent cancers later in life. Polyps have a tendency to bleed and screening for sub-microscopic amounts
of blood can bring them to your doctor’s attention.
Sigmoidoscopy –
Similar to colonoscopy but only examines the lowermost part of the bowel using a rigid rather than a flexible scope. Generally
used if there is fresh blood in the faeces suggesting that the bleeding is coming from the last part of the bowel.
Sensitivity –
If 1000 people are screened with an FOB test and only 10 of those people have a colon cancer or polyp, if all 10 people have
a positive test, the sensitivity of the test is 100%. If 9 of the 10 people with a cancer or polyp have a positive test then
the sensitivity is 90%. The sensitivity of the Actim FOB test is around 89% so that nearly all, the people with a disease
will be detected. No screening test is 100% accurate.
Specificity –
If 990 of 1000 people tested with an FOB test do not have a cancer or a polyp but 90 of them have a positive test then the
specificity is 91% (900/990). You can see that even when the test specificity is very good, many people can have tests that
are falsely positive. In this example there are nearly 10 times more people with positive screening tests that do not have
disease than do have disease. Unfortunately this is the nature of screening. Very highly specific screening tests are rare.
Virtual colonoscopy
– A modern version of colonoscopy that is done by imaging the bowel from outside the body. This test is very attractive
because no instrument has to be inserted into the body but it is not widely available yet except in a few private centres.
