• Bowel cancer screening meets the criteria for a viable, effective, and appropriate screening programme. In particular:
• Bowel cancer is an important health problem, causing approximately 16,000 deaths per year.
• Bowel cancer may be detected at an asymptomatic stage by a simple, safe, and validated screening test that is generally acceptable to the population.
• Early treatment of bowel cancer leads to better outcomes.
• Bowel cancer screening can be be effectively implemented within the NHS.

• A testing kit complete with full instructions (pdf) is sent out 1 week after an invitation for screening.
• Two samples are collected from each of three separate bowel motions by the person at home, using the cardboard sticks provided.
• One of three flaps on the testing kit is peeled back for each bowel motion. A sample is applied to each of the two exposed windows before resealing the window.
• Once all six windows have been used the kit is returned for analysis.
• The kit must be returned within 14 days of the first sample being taken.

[NHS Bowel Cancer Screening Programme, 2006]

• The result of a single screening test is considered to be:
• Clearly normal if none of the six samples taken are positive for faecal occult blood.
• Clearly abnormal if five or six of the samples taken are positive for faecal occult blood.
• Unclear if one to four of the six samples taken are positive for faecal occult blood.
• For people with a single unclear test result, up to two further tests may be required for clarification. Subsequently:
• Screening is considered normal if:
• The initial screening test is clearly normal, or
• An initial screening test was unclear, but two subsequent screening tests are normal.
• Screening is considered abnormal if:
• The initial screening test is clearly abnormal, or
• An initial screening test is unclear, and one of two subsequent screening tests is unclear or clearly abnormal.
• If there is a technical problem in processing the kit or the kit is unreadable owing to incorrect use, participants are sent a letter explaining the problem and a replacement kit.

[NHS Bowel Cancer Screening Programme, 2006]

People with an abnormal faecal occult blood test (FOBt) result

• People with an abnormal FOBt result who have not previously been screened have approximately:
• A 10% chance of having a bowel cancer, and
• A 40% chance of having a benign polyp, which may progress to a malignant lesion if left untreated.
• People with an abnormal FOBt result who had a normal FOBt result within the past 2 years have approximately:
• A 5% chance of having a bowel cancer, and
• A 25% chance of having a benign polyp, which may progress to a malignant lesion if left untreated.

People with a normal FOBt result

• A proportion of people with a normal FOBt result will have bowel cancer, but the risk of cancer after a normal FOBt result is unknown because no studies have compared FOBt with a gold-standard investigation, such as colonoscopy, to accurately determine the specificity or negative predictive value of FOBt screening.

People with colorectal cancer

• An estimated 60% of people with colorectal cancer will have an abnormal FOBt screening result.

People with an abnormal screening result will be:

• Sent a letter explaining the result, with an appointment at a nurse-run clinic within 1 week. A copy of this letter will be sent to the GP.
• Offered colonoscopy; occasionally, other imaging techniques may be offered if colonoscopy is inappropriate.
• People with a suspicious lesion should either have the lesion removed entirely or have sufficient biopsy samples taken to clearly determine the nature of the lesion.
• If biopsy confirms colorectal cancer, the person will be seen at a nurse-run clinic to discuss the result face to face and referred urgently to a named specialist.
• If biopsy confirms a benign lesion, the person will informed of the result by letter within 3 weeks.
• People with benign polyps will usually have these removed. Polyps are classified into low, medium, or high risk depending on the number and size of polyps found.
• People with low-risk polyps are offered further FOBt screening every 2 years, up until the age of 70 years.
• People with medium-risk polyps are offered colonoscopy every 3 years until two examinations are negative.
• People with high-risk polyps are offered repeat colonoscopy after 1 year and then colonoscopy every 3 years until two examinations are negative.
• People with no abnormality detected by complete colonoscopy will be offered further FOBt screening every 2 years, until they are 70 years of age.
• People with an incomplete colonoscopy due to technical difficulties may be offered repeat colonoscopy or another imaging technique.

[NHS Bowel Cancer Screening Programme, 2006]

• People with a normal screening result will:
• Receive a letter explaining the result and information about the symptoms and signs of bowel cancer to look out for in the future.
• Be offered further faecal occult blood test screening every 2 years, until they are 70 or 74 years of age, depending on the maximum age range being used in their area.

[NHS Bowel Cancer Screening Programme, 2006]

• Anxiety over false-positive screening results.
• Complications of colonoscopy, including:
• Heavy bleeding — occurs in approximately 1 in 600 people.
• Bowel perforation — occurs in approximately 1 in 1200 people.
• Death — occurs in approximately 1 in 14,000 people.
• Inappropriate reassurance from a negative screening result may lead people to ignore symptoms of bowel cancer unless they understand the limitations of screening. To reduce the risk of this occurring:
• Written information about the limitations of the screening test, and the symptoms of bowel cancer, is provided before the faecal occult blood test kit is sent.
• Information about the symptoms of bowel cancer to be looked for is again provided when people are informed of a normal screening result.

• A patient information leaflet entitled Bowel cancer: the facts can be ordered or downloaded from the NHS cancer screening website. It is available in:
• 20 languages.
• An audio CD set.
• British sign language.
• A large print version.