The significance of an abnormal faecal occult blood test (FOBt) result

• For people with an abnormal FOBt result who have not previously been screened, the chance that they will have bowel cancer or a benign polyp is based on evidence from the first screening round of the UK Colorectal Cancer Screening Pilot [Weller et al, 2003].
• For people with an abnormal FOBt who had a normal FOBt result within the past 2 years, the chance that they will have bowel cancer or a benign polyp is based on evidence from the second screening round of the english pilot of bowel cancer screening [Weller et al, 2006]. Approximately 80% of people in the second screening round had been screened in the first screening round. This data provides a rough estimate of the risk of cancer for people that have previously been screened.

Estimated sensitivity of FOBt

• The estimated sensitivity of FOBt for detecting bowel cancer in people with the disease has been calculated from data from three good-quality randomized controlled trials in a Cochrane systematic review [Hewitson et al, 2007].
• It was calculated from the number of people known to have had an abnormal FOBt result and an estimate of the true number of people with bowel cancer.
• The true number of people with bowel cancer at the time of screening was estimated from the number of people with bowel cancer detected by screening plus the number of people who developed bowel cancer within 2 years of being screened.