How often should Fecal Occult Blood Test (FOBT) be performed?

Frequency of Fecal Occult Blood Testing (FOBT) for Colorectal Cancer Screening

FOBT should be performed annually for average-risk individuals aged 50-75 years as part of colorectal cancer screening. 1

Recommended Screening Protocol

The most recent and comprehensive guidelines recommend the following approach for FOBT:

• Test frequency: Annual testing
• Collection method: Two samples from each of 3 consecutive stools
• Processing: Without rehydration
• Follow-up: Patients with a positive test on any specimen should undergo colonoscopy 1

Testing Specifics

When performing FOBT, clinicians should:

• Use either a guaiac-based test with dietary restriction or an immunochemical test without dietary restriction 1
• Avoid in-office single-panel guaiac FOBT using a stool sample collected during digital rectal examination due to its low sensitivity 1
• Use newer, high-sensitivity guaiac FOBT (e.g., Hemoccult SENSA) or fecal immunochemical testing (FIT) instead of older, lower-sensitivity versions 1

Evidence Supporting Annual FOBT

Annual FOBT has strong evidence supporting its effectiveness:

• Randomized controlled trials show that annual FOBT reduces colorectal cancer mortality by 33% after 13 years 1
• While a single FOBT has low sensitivity (30-50% range), a program of repeated annual testing can detect up to 92% of cancers 1
• Annual testing is more effective than biennial testing, which only reduces colorectal cancer deaths by 15-21% 1

Alternative Screening Options

While annual FOBT is recommended, guidelines also present other acceptable screening options:

1. Annual high-sensitivity FOBT or FIT
2. Flexible sigmoidoscopy every 5 years
3. Annual FOBT or FIT plus flexible sigmoidoscopy every 5 years
4. Colonoscopy every 10 years
5. Double-contrast barium enema every 5 years
6. CT colonography every 5 years 1

Special Considerations

High-Risk Individuals

More intensive surveillance is recommended for:

• Individuals with a history of adenomatous polyps
• Individuals with a personal history of colorectal cancer
• Individuals with a family history of colorectal cancer or adenomas
• Patients with inflammatory bowel disease 1

These high-risk individuals should begin screening earlier and may require more frequent testing based on their specific risk factors.

Common Pitfalls to Avoid

1. Improper specimen collection: Emphasize to patients the importance of following manufacturer's instructions for specimen collection to ensure accurate results 1

2. Using outdated testing methods: The older, lower-sensitivity versions of guaiac tests should be replaced with newer high-sensitivity tests 1

3. Inadequate follow-up: All positive FOBT results must be followed up with colonoscopy, as this was the diagnostic procedure used in clinical trials showing mortality benefit 1

4. Single in-office testing: Avoid performing single-panel guaiac FOBT during digital rectal examination due to its low sensitivity for advanced adenomas and cancer 1

5. Failure to maintain annual screening: The effectiveness of FOBT depends on regular annual screening, as a single test has limited sensitivity 1