How should I write an order for a fecal occult blood test (FOBT)?

How to Write an Order for Fecal Occult Blood Testing

Order a home-based fecal immunochemical test (FIT) with annual collection, or if FIT is unavailable, order a high-sensitivity guaiac-based FOBT (gFOBT) with proper 3-day home collection from consecutive bowel movements—never order a single-sample office test collected during digital rectal examination. 1, 2

Preferred Test Selection

• FIT is the preferred first-line test because it requires no dietary restrictions, detects only human hemoglobin (eliminating false positives from diet), and has superior diagnostic performance (AUC 0.87) compared to gFOBT (AUC 0.77). 2, 3
• If FIT is unavailable, order high-sensitivity gFOBT (such as Hemoccult SENSA), which has proven mortality reduction of 15-33% in randomized controlled trials. 1, 2

Correct Order Components for FIT

Write the order as:

• "Fecal immunochemical test (FIT) for colorectal cancer screening"
• Specify: "Annual collection from consecutive bowel movements at home"
• Include: "Patient to mail sample to laboratory for processing"
• Note: "No dietary or medication restrictions required" 1, 2

Correct Order Components for High-Sensitivity gFOBT

Write the order as:

• "High-sensitivity guaiac-based fecal occult blood test (gFOBT) for colorectal cancer screening"
• Specify: "Collect 2 samples from each of 3 consecutive bowel movements at home (total 6 samples)"
• Include pre-test instructions:
  • Avoid NSAIDs and aspirin >1 adult dose daily for 7 days before testing 1, 2
  • Avoid vitamin C >250 mg for 3 days before testing 2
  • Avoid red meat, poultry, fish, and some raw vegetables for 3 days before testing 1, 2
• Specify: "Process in clinical laboratory (not office-based)" 1

Critical Pitfalls to Avoid

• Never order single-sample FOBT collected during digital rectal examination—this method has only 4.9% sensitivity for advanced neoplasia and 9% for cancer, providing false reassurance. 2, 4
• Despite 31.2% of physicians using this inadequate method, it is explicitly not recommended by the American Cancer Society, USPSTF, and all major guideline bodies. 2, 4
• Never order FOBT for hospitalized patients or emergency department use—FOBT was developed exclusively for outpatient colorectal cancer screening and has no role in evaluating melena, hematochezia, anemia, or acute GI bleeding. 5, 6

Follow-Up Protocol to Include in Order

• Any positive result requires colonoscopy within 60 days—never repeat the FOBT. 2, 7
• Include standing order: "If positive, schedule colonoscopy to examine entire colon within 60 days" 2, 7
• Each month of delay beyond 60 days increases colorectal cancer incidence by 0.3% and mortality by 1.4%. 7
• A 12-month delay increases cancer incidence by 4% and mortality by 16%. 7

Patient Age and Screening Context

• Order for asymptomatic average-risk adults aged 45-75 years (American Cancer Society lowered starting age to 45 in 2018). 1
• For ages 76-85, individualize based on life expectancy, health status, and prior screening history. 1
• Do not order for patients >85 years unless no prior screening and excellent health status. 1

Quality Assurance Elements

• Ensure your electronic health record system includes reminder mechanisms for test completion and return—only 44.3% of physicians have such systems, contributing to poor screening rates. 4
• Build in automatic colonoscopy referral triggers for positive results to prevent the common error of repeat FOBT (still practiced by 17.8% of physicians). 4