High yield of colorectal neoplasia detected by colonoscopy following a positive faecal occult blood test in the NHS Bowel Cancer Screening Programme

Objectives The UK National Health Service Bowel Cancer Screening Programme (BCSP) is based on a strategy of biennial faecal occult blood (FOB) testing. Positive results are classified as 'abnormal' or 'weak positive' based on the number of positive windows per kit or need for repeat testing. Colonoscopy is offered to both groups. We evaluate the relationship between FOB test positivity and clinical outcome in the BCSP. Setting The South of Tyne and Tees (UK) Bowel Cancer Screening Centres. Methods Data were collected prospectively on all individuals who were offered FOB testing and colonoscopy between February 2007 and February 2009. Univariable and multivariable analyses were performed to investigate the relationship between FOB test positivity and clinical outcome. Results Following FOB testing, 1524 individuals underwent colonoscopy, 1259 (83%) after a 'weak positive' and 265 (17%) an 'abnormal' result. Cancer was detected in 180 (11.8%) and adenomas in 758 (49.7%). Individuals with an 'abnormal' result were more likely to have cancer or be 'high risk' for the development of future adenomas (110/265, 41.5%) than those with 'weak positive' results, (236/1259, 18.7%, P < 0.0001). Those with Dukes stage B, C or D cancers or cancers proximal to the splenic flexure were more likely to have an 'abnormal' result. Conclusions The majority of colonoscopies were performed following 'weak positive' FOB results. Those with an 'abnormal' result were more likely to be diagnosed with cancer. The high yield of pathology in both the 'abnormal' and 'weak positive' groups justifies the need for colonoscopy in both.