FOBT Flashcards
(15 cards)
FOBT may be indicative of
Asymptomatic gastrointestinal diseases like:
- colorectal cancer
- polyps
- colitis
Any bleeding in excess of _________ of stool is considered pathologically significant, and no visible signs of bleeding may be present with this amount of blood
2.5mL/150g
Annual testing for occult blood has a high positive predictive value for detecting colorectal cancer in the early stages and is recommended for people over ______ years of age by _____
50 years
American Cancer Society
Principle of OFBT
It detects blood in stool by using the pseudoperoxidase activity of hemoglobin to react with hydrogen peroxide, oxidizing a colorless compound (guaiac) to a colored compound (oxidized guaiac)
Patients with bleeding from other conditions such as _____ should not be tested while such conditions are present
- Hemorrhoids
- Dental work
- Constipation
- Menstrual bleeding
Positive result of the test
Any trace of blue, read after 30 seconds and before 2 minutes
This test will detect ______ of hemoglobin per gram of fecal material
10mg
Normal stool can contain up to _____ of blood
2.5mL
Causes false negative result; strong reducing agent that interferes with the peroxidase reaction
Ascorbic acid in high doses (>250 mg/day)
Causes false negative result; discontinue intake for 3 days before collection and during the test period
Iron supplements containing Vitamin C
Contains dietary pseudoperoxidase
Red meat
Avoid these food 3 days before specimen collection and continuing through the test period
Fruits and vegetables such as:
- Turnips
- Broccoli
- Horseradish
- Cauliflower
- Radishes
- Melons
May cause bleeding or irritation of the GI tract
Discontinue for 7 days before specimen collection and during the test period
Aspirin and NSAIDS other than acetaminophen
Alcoholic drinks
3 methods
- Immunochemical
- Fluorometric porphyrin (most sensitive and specific)
- Guaiac test (most common)
Other chromogens used
Benzidine (most sensitive)
Guaiac (preferred)
O-toluidine
