What foods can cause a false-positive occult blood test?
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).
Some of the more common causes include colon cancer, esophagitis, peptic ulcers, gastritis, inflammatory bowel disease, vascular ectasias, portal hypertensive gastropathy, gastric antral vascular ectasias, and small bowel tumors (eg, GI stromal cell tumor, lymphoma, carcinoid, adenocarcinoma, or polyp).
What does a positive fecal occult blood test mean? If your FOBT is positive, there could be bleeding in your digestive tract. It may signal colorectal cancer, but it isn't a cancer diagnosis. Typically, if the result is positive, your provider will call you to talk about next steps.
Another group of studies which had been evaluated for the accuracy of FOBT, the pooled sensitivity was 31% (95% CI: 25, 38%) while the pooled specificity was 87% (95% CI: 86, 89%).
Because several other situations can lead to blood in the stool, a positive FOBT does not necessarily mean that cancer is present. Hemorrhoids, anal fissures, constipation or inflammatory bowel disease can also cause blood in the stool.
A positive result on a fecal occult blood test doesn't mean you have cancer. Other health conditions, such as ulcers or hemorrhoids, more commonly can cause a positive test result. Healthcare providers will do more tests find the cause.
Your test could show a positive result when you have no cancer (false-positive result) if you have bleeding from other sources, such as a stomach ulcer, hemorrhoid, or even blood swallowed from your mouth or your nose. Having a fecal occult blood test may lead to additional testing.
“Sometimes blood in the stool can be caused by benign conditions such as hemorrhoids, a small fissure after constipation or an infection and can resolve on its own,” he says. “However, bleeding from cancer or inflammatory bowel disease can also be intermittent, and so any bleeding needs to be investigated.”
Treatment of bleeding most often involves endoscopic ablation of the bleeding site with thermal energy, if the site is accessible. Angiographic embolization may be used to treat lesions that cannot be reached endoscopically.
A doctor may request a fecal occult blood test to look for blood that's present due to causes such as: allergies or inflammation. gastrointestinal infection caused by bacteria, viruses, or parasites. bleeding in the GI tract from ulcers and other problems.
What conditions would necessitate testing a patient's stool for occult blood?
Why do I need a fecal occult blood test? Your health care provider may order a fecal occult blood test if you have symptoms of a condition that could involve bleeding in your digestive tract. Or you may have the test to screen for colorectal cancer when you don't have any symptoms.
A blue or blue-green color should be interpreted as positive for occult blood.
In vitro testing confirmed that ferrous compounds caused a false-positive Hemoccult slide reaction. Previous studies of the effect of medicinal iron on occult blood tests are reviewed.
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.
Immunochemical faecal occult blood test (iFOBT)[edit source]
All studies consistently reported a sensitivity of greater than 50%, with most studies reporting sensitivities in the 60–85% range. Specificity was consistently high across all 20 studies and ranged from 85% to 100%.
Abstract. Occult gastrointestinal bleeding commonly manifests as iron deficiency anemia or fecal occult blood. Iron deficiency anemia results from chronic occult gastrointestinal bleeding.
Because the intake of iron, bismuth or foods like beets can give the stool the same appearance as bleeding from the digestive tract, a doctor must test the stool for blood before offering a diagnosis. Other symptoms: Bright red blood coating the stool. Dark blood mixed with the stool.