Fecal Occult Blood Test

• The Fecal Occult Blood Test (FOBT) detects microscopic amounts of blood in stool, which may not be visible to the naked eye.
• It is primarily used as a screening tool for colorectal cancer and other gastrointestinal issues.
• Preparation for the test involves dietary restrictions and avoiding certain medications to ensure accurate results.
• Positive results indicate the presence of blood but require further diagnostic tests to determine the cause.
• Regular screening with FOBT can significantly improve outcomes for conditions like colorectal cancer through early detection.

What is a Fecal Occult Blood Test (FOBT)?

A Fecal Occult Blood Test (FOBT) is a non-invasive laboratory test designed to detect microscopic amounts of blood in a person’s stool that are not visible to the naked eye. The presence of occult blood can indicate bleeding anywhere along the gastrointestinal (GI) tract, from the esophagus to the colon. This bleeding might be a symptom of various conditions, including polyps, ulcers, hemorrhoids, diverticulosis, or, most critically, colorectal cancer.

The FOBT meaning and procedure typically involves collecting small stool samples over several days at home. These samples are then sent to a laboratory for analysis. There are generally two main types of FOBT: guaiac-based FOBT (gFOBT) and immunochemical FOBT (iFOBT or FIT). Guaiac tests detect the heme component of hemoglobin using a chemical reaction, while immunochemical tests specifically detect human hemoglobin, making them less prone to interference from animal blood or certain foods. According to the American Cancer Society, regular screening can reduce the risk of dying from colorectal cancer.

Why is FOBT Done and How to Prepare?

The Fecal Occult Blood Test is primarily done as a screening method for colorectal cancer, particularly in individuals aged 45 and older who are at average risk. Early detection of colorectal cancer significantly improves treatment outcomes and survival rates. Beyond cancer screening, FOBT may also be performed to investigate unexplained anemia, changes in bowel habits, or other symptoms suggestive of gastrointestinal bleeding. It serves as an initial step to identify potential issues that may warrant more invasive diagnostic procedures, such as a colonoscopy.

Proper preparation is crucial for accurate FOBT results. The specific instructions can vary slightly depending on the type of test (gFOBT vs. iFOBT) and the healthcare provider. However, general guidelines for how to prepare for FOBT often include dietary restrictions and medication adjustments for a few days before and during the stool collection period.

Here are common preparation guidelines:

• Dietary Restrictions (especially for gFOBT): Avoid red meat (beef, lamb, pork) for 2-3 days prior to and during the test, as it contains animal blood that can lead to false-positive results. Limit foods high in vitamin C (e.g., citrus fruits, broccoli) and certain vegetables (e.g., turnips, radishes) as they can interfere with gFOBT results. Increase fiber intake to promote regular bowel movements.
• Medication Adjustments: Discontinue aspirin, non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, and iron supplements for several days before the test, as they can cause GI bleeding or interfere with results. Always consult your doctor before stopping any prescribed medication. Avoid vitamin C supplements in high doses.
• Other Considerations: Do not collect samples during menstruation or if you have bleeding hemorrhoids, as this can lead to false positives. Avoid using toilet bowl cleaners that might contaminate the sample. Follow the specific instructions provided by your healthcare provider regarding sample collection and storage precisely.

A positive FOBT result does not confirm cancer but indicates the need for further investigation, typically a colonoscopy, to identify the source of bleeding. Conversely, a negative result does not entirely rule out the presence of polyps or cancer, as not all lesions bleed continuously. Regular screening, as recommended by organizations like the Centers for Disease Control and Prevention (CDC), is key for effective colorectal cancer prevention and early detection.