FITscreening

FIT screening, or the fecal immunochemical test screening, is a noninvasive method used in colorectal cancer screening. It uses a fecal immunochemical test to detect hidden human blood in stool, which can be an early sign of colorectal cancer or advanced adenomas. FIT screening is commonly implemented in population-based programs due to its ease of use and noninvasive nature.

The test detects human hemoglobin in stool by antibodies, making it more specific for bleeding from the colorectum and less affected by diet than guaiac-based tests. Samples are collected at home using a kit, often requiring one or two small samples on different days. The specimen is sent to a laboratory where the assay reports a qualitative positive/negative result or a quantitative level that may be used to set a positivity threshold.

Guidelines for FIT screening vary by country but typically target average-risk adults starting in the late 40s to early 50s and continuing into the mid-70s or beyond. Screening intervals are commonly annual or every two years. A positive FIT result requires diagnostic follow-up with colonoscopy to identify and potentially remove cancers or advanced polyps.

Advantages include higher specificity for colorectal bleeding, no dietary restrictions, ease of use, and potential to improve participation compared with invasive tests. Limitations include that FIT is not diagnostic and may miss nonbleeding cancers or lesions, and results can be influenced by test threshold, sample handling, or intermittent bleeding. Access to colonoscopy and compliance with follow-up are critical to effectiveness.