Does iron affect guaiac?
Most studies show that oral ingestion of iron does not cause a positive stool guaiac reaction. However, all in vitro studies show that iron does cause a positive guaiac reaction and some in vivo studies have shown a positive stool guaiac reaction in response to oral iron.
Can iron supplements cause false-positive Hemoccult?
The Hemoccult methods had 65% and 50% false-positive reactions while the Hematest had 25% and 65% false-positive reactions after ferrous sulfate and ferrous gluconate, respectively. In vitro testing confirmed that ferrous compounds caused a false-positive Hemoccult slide reaction.
Does iron affect occult blood test?
The general agreement in the literature is that oral iron supplementation does not cause a false-positive guaiac-based fecal occult blood test (GFOBT).
Can iron supplements cause FOBT positive?
Iron will not affect FOBT results in vivo. Ascorbic acid might inhibit positive FOBT results both in vitro and in vivo, but it has not been studied in screening populations.
What can cause a false-positive guaiac test?
The test can actually be positive for up to 2 weeks after an acute bleed and thus is more useful for diagnosing chronic occult bleeding. Uncommonly, false-positive results can be triggered by ingestions of red meat, turnips, horseradish, vitamin C, methylene blue, and bromide preparations.
Does iron cause false-positive?
What can cause a false-negative guaiac test?
Additionally, guaiac FOBTs are prone to false-negative results, and the classic causative substance is ascorbic acid (vitamin C). Ascorbic acid is a strong reducing agent that blocks the oxidative guaiac reaction.
What food can cause a false-positive occult blood test?
Any cooked fruits and vegetables High fiber foods (e.g. whole wheat bread, bran cereal, popcorn). Foods, Drugs, and Vitamins to Avoid: Red meat (beef, lamb), including processed meats and liver. Any raw fruits and vegetables (especially melons, radishes, turnips and horseradish).
Which foods cause false-negative guaiac test?
Decreased guaiac test sensitivity was associated with activated charcoal, dimethylaminoethanol, red chile, N-acetylcysteine, rifampin, red Jell-O (General Foods Corp, White Plains, NY), orange juice, Pepto-Bismol (Norwich Eaton Pharmaceuticals, Norwich, NY), simethicone, spaghetti sauce, and several red wines.
What can alter a guaiac test?
What can cause a false-positive stool test?
False-positive results have been associated with red or rare meat as well as raw fruits and vegetables, including but not limited to horseradish, raw turnips, cantaloupe, broccoli, cauliflower, parsnips, and red radishes.
What causes false negative stool occult blood?
False-negative stool occult blood tests caused by ingestion of ascorbic acid (vitamin C)
What should I avoid before guaiac test?
Some medicines may interfere with the test. These include vitamin C, aspirin, and NSAIDs such as ibuprofen and naproxen. Ask your health care provider if you need to stop taking these before the test….These may include:
- Red meat.
- Uncooked broccoli.
What causes false-positive guaiac test?
What food can cause a false-positive guaiac test?
VI. Causes: False Positive Guaiac tests (Hemoccult)
- Red meat.
- Cantaloupe and other melon.
What food can cause a false-negative guaiac test?
What foods can cause a false-negative guaiac test?
Does iron cause a positive guaiac reaction?
However, all in vitro studies show that iron does cause a positive guaiac reaction and some in vivo studies have shown a positive stool guaiac reaction in response to oral iron. This study examines this un …
Does oral iron supplementation cause false positive guaiac-based fecal occult blood test (gFOBT)?
July 31, 2017. The general agreement in the literature is that oral iron supplementation does not cause a false-positive guaiac-based fecal occult blood test (GFOBT).
How to use the guaiac test?
Both sides of the test card can be peeled open, to access the inner guaiac paper. One side of the card is marked for application of the stool and the other is for the developer fluid. After applying the feces, one or two drops of hydrogen peroxide are then dripped on to the other side of the film, and it is observed for a rapid blue color change.
What are guaiac and immunochemical fecal occult blood tests?
Both the guaiac and immunochemical fecal occult blood tests detect hidden blood in the stool collected by patients using kits used in their homes. Each test has a unique set of directions that must be followed to assure that the stool is collected properly and there is enough sample for the pathologists to conduct their analysis.