What Causes a Positive Fecal Occult Blood Test?

A positive fecal occult blood test indicates the presence of blood in the stool that is not visible to the naked eye or under a microscope. This occurs when hemoglobin, specifically the heme component, is released from broken-down red blood cells and is detected through chemical testing. A positive result can occur due to bleeding anywhere along the digestive tract—from the mouth, nose, esophagus, stomach, intestines, and even the anus. If the blood loss exceeds 5 ml, it may lead to a positive test result. The most common cause of a positive fecal occult blood test is gastrointestinal bleeding, which may stem from conditions such as peptic ulcers, gastric mucosal injury, gastrointestinal tumors, colitis, or Crohn's disease.

However, it's important to note that a positive result does not always mean there is actual bleeding in the digestive system. Certain foods and medications can cause false-positive results. For example, consuming organ meats, pork blood, duck blood, or large amounts of spinach may lead to an inaccurate positive reading. Similarly, taking iron supplements or bismuth-containing medications can also affect the test outcome. To ensure accurate results, patients are advised to avoid consuming blood-containing foods, liver products, and iron supplements for at least three days before the test.

If a person consistently tests positive for occult blood in the stool, it is crucial to investigate further. Repeated positive results may indicate a serious underlying condition, including the possibility of gastrointestinal cancer. In such cases, doctors often recommend additional diagnostic procedures like gastroscopy or colonoscopy to identify the exact source and cause of the bleeding. These tests are essential for making an accurate diagnosis and determining the most effective treatment plan. Early detection and intervention can significantly improve health outcomes, especially when serious conditions like tumors are involved.

In summary, while a positive fecal occult blood test can be concerning, it is not always a sign of a severe illness. Proper preparation before testing and follow-up evaluations are key to understanding the true cause behind the result. Always consult with a qualified healthcare professional for proper guidance and care.