Utility of fecal immunochemical test vs guaiac fecal occult blood test for assessment of gastrointestinal bleed in hospitalized patients.

Background: Guaiac fecal occult blood testing (gFOBT) is often used "off-label" for gastrointestinal (GI) bleeding. Fecal Immunochemical Test (FIT) is increasingly replacing gFOBT in colorectal cancer screening and may play a role in assessment for significant bowel disease. We examined the concordance of FIT with gFOBT (Hemoccult Sensa II) among inpatients and between day 1 and day 3 gFOBT results.

Methods: FIT was performed alongside gFOBT on all inpatient stool sent for occult blood to the Winnipeg Health Sciences Centre laboratory over 1 y. gFOBT was performed on days 1 and 3 post stool collection, while FIT was performed on day 1 only.

Results: Positivity rates were highest for Day 1 gFOBT (27.7%), and lowest for FIT (18.3%). Concordance between FIT and Days 1 and 3 gFOBT for negative test results (96.4% and 94.1%) was significantly higher than that expected by chance alone (58.7% and 61.3%, P < .001). Similarly, concordance for positive test results (55.8% and 55.6%) was significantly higher as well as for days 1 and 3 gFOBT results.

Conclusions: We found no benefit in delayed testing for 3 days post collection. FIT provides equivalent results to gFOBT in hospitalized patients.