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How often are FOBTs positive in the NBCSP?

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How often are FOBTs positive in the NBCSP?

About 1 in 14 patients (7%) have a positive FOBT and most of these patients require further investigation as they are 12 times more likely to have colorectal cancer than patients with negative tests. In FOBT positive patients, 6% are found to have bowel cancer, 14% advanced adenomas, and 35% polyps. It is important to realise that a negative FOBT does not exclude cancer (it only detects blood, if present, in the stool, not polyps or cancer), so a symptomatic patient should be referred for colonoscopy without having a FOBT performed as a negative test may lull the patient or doctor into a false sense of security. Similarly it is recommended that patients already enrolled in surveillance programmes for follow-up of colonic polyps should not have regular FOBTs as a means of deciding whether to proceed with their follow-up investigation or not.