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Colorectal screening - Management
What is the significance of a normal/abnormal screening test?
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.
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