Fecal Immunochemical Test (FIT) for Gastrointestinal Bleeding Detection

Types of Stool Tests

The American College of Physicians recommends the fecal immunochemical test (FIT) as the preferred stool examination for detecting gastrointestinal bleeding due to its superior sensitivity, specificity, and lack of dietary restrictions compared to other stool tests 1
FIT specifically detects human hemoglobin in stool, making it highly specific for human blood 1
The US Preventive Services Task Force recommends FIT for colorectal cancer screening in adults aged 45 years and older 1
Guaiac-based fecal occult blood test (gFOBT) requires dietary restrictions before testing, such as avoiding red meats, certain vegetables, vitamin C, and NSAIDs 2
High-sensitivity gFOBT is still recommended as an option for colorectal cancer screening, although it is less sensitive and specific than FIT 1

The American Cancer Society recommends using stool tests, such as FIT, as part of colorectal cancer screening for average-risk adults aged 45 years and older 1, 3
FIT is useful in evaluating patients with iron deficiency anemia of unknown origin, as recommended by the National Comprehensive Cancer Network 4 is not used, instead: The guideline society recommends using FIT to evaluate occult gastrointestinal bleeding when the source is unclear 5, 6
Any positive stool test for blood requires follow-up with colonoscopy, as recommended by the National Comprehensive Cancer Network 3
For patients with persistent bleeding and negative colonoscopy, upper endoscopy should be performed to evaluate for upper GI sources, as recommended by the American Gastroenterological Association 5, 6

Single stool sample collected during digital rectal examination is not recommended due to poor sensitivity, as stated by the American Cancer Society 2
Specimens should be collected from successive bowel movements over multiple days for optimal sensitivity, as recommended by the American Cancer Society 2
For active, visible bleeding, direct visualization tests (colonoscopy, CT angiography) are preferred over stool tests, as recommended by the Radiological Society of North America and the European Society of Gastrointestinal Endoscopy 7, 8