How often should I do a Fecal Occult Blood Test (FOBT)?

Fecal Occult Blood Test (FOBT) Screening Frequency

For average-risk individuals, fecal occult blood testing (FOBT) should be performed annually beginning at age 50. 1

Screening Recommendations by Risk Category

Average-Risk Individuals:

• Begin screening at age 50 1, 2
• Annual FOBT is the recommended frequency 1
• Continue screening until age 75 1, 2
• After age 75, individualize decisions based on prior screening history and overall health 2

High-Risk Individuals:

• Begin screening at age 40 (or earlier) for those with:
  • Family history of early colorectal cancer 1
  • First-degree relatives with colorectal cancer 1
  • Hereditary syndromes (familial polyposis, hereditary non-polyposis colorectal cancer) 1
  • Inflammatory bowel disease 1
• More frequent screening may be necessary (consult specialist) 1

Types of FOBT Available

• High-sensitivity guaiac FOBT (e.g., Hemoccult SENSA): Preferred over older low-sensitivity versions 1
• Fecal immunochemical test (FIT): Superior to guaiac FOBT for detection rates and positive predictive value 1
• FIT-DNA test: Recommended every 1-3 years 2

Important Considerations

Proper Testing Technique

• At-home testing requires following manufacturer's instructions precisely 1
• In-office single-panel guaiac FOBT using a stool sample collected during digital rectal examination is NOT recommended due to low sensitivity 1
• Collect two samples from three consecutive bowel movements for proper testing 1

Effectiveness and Limitations

• Annual FOBT reduces colorectal cancer mortality by 15-33% 1, 2, 3
• FOBT has lower sensitivity for polyps, especially smaller ones 3
• After 10 years of annual screening, approximately 23% of patients will experience at least one false-positive result 4
• FOBT as a sole screening method may miss some cancers, particularly advanced left-sided colorectal cancers 5

Alternative and Complementary Screening Options

• FOBT plus flexible sigmoidoscopy every 5 years is an effective combined approach 1, 3
• Other screening options include:
  • Colonoscopy every 10 years 1
  • Flexible sigmoidoscopy every 5 years 1
  • Double-contrast barium enema every 5 years 1
  • CT colonography every 5 years 1, 2

Follow-up of Positive Results

• Any positive FOBT result requires follow-up with colonoscopy 1, 3
• Prompt diagnostic workup following positive tests leads to treatment of earlier stage cancers and increased survival 6

Key Pitfalls to Avoid

• Don't rely solely on in-office single-sample FOBT during digital rectal examination 1
• Don't assume a negative FOBT completely rules out colorectal cancer; it has limitations in detecting certain cancers 5
• Don't skip follow-up colonoscopy after a positive FOBT result 3
• Don't use toilet bowl FOBT tests as they are not recommended 1

Remember that while there are multiple screening options available, the most important factor is adherence to a regular screening schedule. Annual FOBT is a practical, non-invasive option that has demonstrated effectiveness in reducing colorectal cancer mortality when performed correctly and consistently.