The faecal immunochemical test (FIT) is used in colorectal cancer screening to detect hidden blood in faeces, which may indicate colorectal cancer or advanced adenomas. A positive FIT result, defined as a faecal haemoglobin concentration of at least 10 micrograms of haemoglobin per gram of faeces, should prompt a suspected cancer pathway referral for further investigation, typically colonoscopy, to confirm or exclude colorectal cancer.
A negative FIT result does not completely exclude colorectal cancer, as no screening test is 100% effective; interval cancers can occur between screening rounds. Therefore, clinicians should not be over-reassured by a previous negative FIT result if symptoms persist or worsen.
FIT thresholds and interpretation differ between screening and symptomatic contexts, with screening programmes commonly using a cut-off around 20 micrograms haemoglobin/g faeces, but referral thresholds in symptomatic patients are lower (10 micrograms/g) to increase sensitivity.
Primary care teams should promote uptake of FIT screening, as increased participation improves early detection rates, especially in men and across all deprivation groups.