NHA Certified Clinical Medical Assistant (CCMA)Clinical Patient CareMedium
A medical assistant is preparing to perform a fecal occult blood test (FOBT) using a guaiac card. Which of the following foods or medications should the patient be instructed to avoid prior to the test?
- AChicken
- BTylenol (acetaminophen)
- CWhite bread
- DVitamin C supplements
Show answer & explanationAnswer & explanation
Correct answer: D. Vitamin C supplements
Patients should be instructed to avoid certain foods and medications, such as Vitamin C supplements, red meat, and certain vegetables, for several days before a guaiac-based FOBT. Vitamin C is a strong reducing agent that can cause false-negative results by interfering with the chemical reaction.
Why the other options are wrong
- A. Red meat should be avoided, but chicken is generally permissible.
- B. Acetaminophen (Tylenol) does not typically interfere with guaiac FOBT results, although other NSAIDs might.
- C. White bread does not interfere with FOBT results.
FOBT Interference (Guaiac)
Certain substances, notably Vitamin C, red meat, and some medications, can interfere with guaiac-based Fecal Occult Blood Tests (FOBT), leading to false-negative or false-positive results.
- Vitamin C causes false negatives.
- Red meat causes false positives.
- Patient education is critical for accurate results.
Memory trick: FOBT False Alarms: Red Meat, Vitamin C, NSAIDs, Broccoli.