How often should Fecal Occult Blood Tests (FOBT) be performed for colorectal cancer screening?

Frequency of Fecal Occult Blood Testing for Colorectal Cancer Screening

Fecal occult blood tests (FOBT) should be performed annually for colorectal cancer screening in average-risk individuals aged 50-75 years. 1, 2

Types of Fecal Occult Blood Tests

There are two main types of fecal occult blood tests used for colorectal cancer screening:

1. Guaiac-based FOBT (gFOBT):

   • Requires annual testing
   • Needs 3 consecutive stool samples
   • Requires dietary restrictions
   • Only high-sensitivity versions (such as Hemoccult SENSA) should be used 2, 1

2. Fecal Immunochemical Test (FIT):

   • Requires annual testing
   • More specific for human hemoglobin
   • No dietary restrictions needed
   • Better sensitivity and specificity than gFOBT 1, 3

Screening Recommendations by Age Group

• Ages 45-49: The American Cancer Society recommends beginning screening at age 45 2
• Ages 50-75: Annual FOBT is recommended for average-risk individuals 1, 2
• Ages 76-85: Individualize decision based on prior screening history, overall health, and life expectancy 2, 1
• Ages >85: Screening is generally discouraged 2

Proper Testing Technique

For optimal effectiveness, FOBT must be performed correctly:

• Single-sample in-office FOBT during digital rectal examination is NOT recommended due to very low sensitivity 2, 1
• At-home testing requires following manufacturer's instructions precisely 1
• For gFOBT, collect samples from 3 consecutive bowel movements while adhering to dietary restrictions 1
• Any positive FOBT result requires follow-up with colonoscopy 1

Effectiveness of Annual FOBT

• Annual or biennial FOBT reduces colorectal cancer mortality by 15-33% 1, 3
• When properly performed, program sensitivity ranges from 45-54% 1
• Biennial testing with proper technique reduces colorectal cancer mortality by 13-16% 1

Alternative Screening Approaches

While annual FOBT is recommended, other acceptable screening options include:

• Annual FOBT plus flexible sigmoidoscopy every 5 years 2, 1, 4
• Colonoscopy every 10 years 2, 1
• CT colonography every 5 years 2, 1
• Multitarget stool DNA test (FIT-DNA) every 3 years 2, 1

Special Considerations

• For individuals with family history of colorectal cancer, hereditary syndromes, or inflammatory bowel disease, more frequent screening starting at an earlier age (40 or younger) is recommended 1
• The Canadian Task Force on Preventive Health Care recommends FOBT every 2 years, which differs from the annual recommendation in the United States 2

Common Pitfalls to Avoid

1. Don't use single-sample office-based FOBT during digital rectal examination as it has very low sensitivity and high false-negative rates 2, 1
2. Don't use older, lower-sensitivity versions of guaiac tests (such as Hemoccult II) 2
3. Don't rely on toilet bowl tests as they are not recommended for screening 1
4. Don't forget to follow up positive results with colonoscopy 1
5. Don't underestimate the importance of patient adherence to testing protocols, as even the best test is ineffective if patients don't complete it properly 1

The most recent and comprehensive guidelines from the National Comprehensive Cancer Network, American Cancer Society, and U.S. Preventive Services Task Force all support annual FOBT as an effective screening strategy for colorectal cancer when performed correctly.