What are the implications of a positive fecal occult blood test (FOBT)?

From the Guidelines

A positive occult blood test requires prompt follow-up with a healthcare provider for further evaluation, and the most important next step is to schedule a colonoscopy, which is the gold standard for investigating the source of gastrointestinal bleeding. This is based on the most recent and highest quality study available, which emphasizes the importance of colonoscopy in the diagnostic workup of a positive fecal occult blood test (FOBT) result 1.

Key Considerations

• The presence of occult blood could indicate various conditions ranging from benign causes like hemorrhoids to more serious conditions such as colorectal cancer, inflammatory bowel disease, or polyps.
• The bleeding is often intermittent and in small amounts, which is why it's not visible to the naked eye but detectable through chemical testing.
• Early detection and investigation of the cause significantly improves treatment outcomes, especially for conditions like colorectal cancer where early intervention is crucial.
• While waiting for the colonoscopy appointment, it is recommended to avoid taking NSAIDs like ibuprofen or aspirin, as these can cause gastrointestinal irritation and bleeding.
• Temporarily discontinuing iron supplements and vitamin C is also advised, as they can affect test results.
• Maintaining a normal diet before the colonoscopy appointment is recommended, as dietary restrictions are no longer necessary for occult blood testing interpretation.

Evidence-Based Recommendations

• The American College of Physicians recommends selecting the colorectal cancer screening test with the patient based on a discussion of benefits, harms, costs, availability, frequency, and patient preferences 1.
• The guidelines suggest that a positive FOBT result should be followed by a colonoscopy to examine the entire colon and rule out the presence of cancer or advanced neoplasia 2, 3.
• The use of fecal immunochemical testing (FIT) is also recommended, as it has been shown to have better sensitivity and specificity than guaiac-based FOBT 1, 4.

Conclusion Not Provided as per Guidelines

Instead, the key points are summarized above, emphasizing the importance of prompt follow-up and colonoscopy in the management of a positive occult blood test result.

From the Research

Definition and Evaluation of Occult Gastrointestinal Bleeding

• Occult gastrointestinal bleeding is defined as gastrointestinal bleeding that is not visible to the patient or physician, resulting in either a positive fecal occult blood test, or iron deficiency anemia with or without a positive fecal occult blood test 5.
• A stepwise evaluation will identify the cause of bleeding in the majority of patients, with esophagogastroduodenoscopy (EGD) and colonoscopy finding the bleeding source in 48 to 71 percent of patients 5.

Diagnostic Approaches

• The initial work-up for occult bleeding typically involves colonoscopy or esophagogastroduodenoscopy, or both 6.
• In patients without symptoms indicating an upper gastrointestinal tract source or in patients older than 50 years, colonoscopy usually is performed first 6.
• Capsule endoscopy has a diagnostic yield of 61 to 74 percent if a cause is not found after EGD and colonoscopy have been performed 5.
• Deep enteroscopy reaches into the mid and distal small bowel to further investigate and treat lesions found during capsule endoscopy or computed tomographic enterography 5.

Management of Patients with Positive Fecal Occult Blood Test

• Evaluation of a patient who has a positive fecal occult blood test without iron deficiency anemia should begin with colonoscopy; asymptomatic patients whose colonoscopic findings are negative do not require further study unless anemia develops 5.
• All men and postmenopausal women with iron deficiency anemia, and premenopausal women who have iron deficiency anemia that cannot be explained by heavy menses, should be evaluated for occult gastrointestinal bleeding 5.
• Physicians should not attribute a positive fecal occult blood test to low-dose aspirin or anticoagulant medications without further evaluation 5.

Role of Double-Contrast Barium Enema

• Double-contrast barium enema is commonly employed to study the rest of the colon when colonoscopy is incomplete 7.
• Double-contrast barium enema associated to incomplete colonoscopy was responsible for an increase in detection rates of cancer or adenoma of 2.3/1000 or 3.8/1000, respectively 7.
• The diagnostic contribution observed in the present survey confirms the opportunity of performing double-contrast barium enema as a routine adjunct to incomplete colonoscopy 7.