FOBT kits - Immunoassay

Immunoassay FOBT kits are new within the last eight years and have received approval for Medicare reimbursement, but immunoassay does not obsolete Guaiac FOBT kits.  Approximately a half dozen iFOBT kits are on the US market today.

Immunochemical, immunoassay FOBT kits are tests based on more steps & more complicated chemistry which results in a more sensitive detection of hidden blood in fecal matter, but is sensitive only to blood from the lower colon, & not the upper GI tract, which gFOBT kits can detect.

The immunoassay development process is more time consuming, with morse steps and parts in the kit and is sometimes linked to a desktop analyzer, coupled with a much higher cost than Guaiac FOBT kits.

For use in the ICU, Emergency and Surgery Departments, immunoassay FOBT’s higher sensitivity detection (only for the large colon) are at a much higher cost and not the best choice as a first level test, especially when clinicians are concerned about possible GI bleeding anywhere in the GI tract.

GI bleeding itself is often intermittent, and hence multiple FOBT kits are often used on a patient over time to confirm the existence of, start of, or ending of bleeding, and as such Guaiac FOBTs are the first level test most used.