At what age should I start getting an occult stool test, also known as a fecal occult blood test (FOBT), for colorectal cancer screening?

Colorectal Cancer Screening with Fecal Occult Blood Testing

Begin annual fecal occult blood testing (FOBT) at age 50 for average-risk individuals, using a properly collected 3-sample home test kit, not a single office sample. 1

Starting Age for Average-Risk Individuals

• Age 50 is the standard starting age recommended by multiple major guidelines including USPSTF, ACS (prior to 2018), American College of Gastroenterology, and the U.S. Multi-Society Task Force 1

• Age 45 may be considered based on the 2018 ACS update, which lowered the recommended starting age to 45 years as a "qualified recommendation" due to rising colorectal cancer rates in younger adults 1

• African Americans should begin at age 45 according to the U.S. Multi-Society Task Force and American College of Physicians, based on higher overall colorectal cancer risk in this population 1, 2

Testing Frequency and Method

• Annual FOBT is required for effective screening, as one-time testing has inadequate sensitivity 1

• Use high-sensitivity guaiac-based FOBT (like Hemoccult SENSA) or fecal immunochemical test (FIT), not older low-sensitivity versions like Hemoccult II 1, 2

• Properly collected 3-sample home testing is mandatory - samples should be from 3 consecutive bowel movements collected at home following manufacturer instructions 3

• Single-sample office FOBT collected during digital rectal examination should never be used, as it has unacceptably poor sensitivity of only 4.9% for advanced disease 3

Pre-Test Preparation

• Avoid NSAIDs and high-dose aspirin for 7 days before testing 3
• Avoid vitamin C exceeding 250 mg and red meats for 3 days before testing 3
• These restrictions minimize false positive results from dietary pseudoperoxidase activity 3

When to Stop Screening

• Continue screening until age 75 for individuals who are up-to-date with screening 1

• Age 76-85: screening is not routinely recommended but may be considered in select individuals who have never been screened and have good health status 1

• After age 85: screening is not recommended 1

• Discontinue screening when life expectancy is less than 10 years, even if younger than 75 2

High-Risk Individuals Requiring Earlier/More Intensive Screening

Start colonoscopy (not FOBT) at age 40 or 10 years before the youngest affected relative's diagnosis for individuals with:

• One first-degree relative with colorectal cancer or advanced adenoma diagnosed before age 60 1, 4, 2, 5
• Two or more first-degree relatives with colorectal cancer or advanced adenoma at any age 1, 4, 2, 5

Start colonoscopy at age 25 and repeat every 1-2 years for individuals with hereditary nonpolyposis colorectal cancer (Lynch syndrome) 1, 5

Start screening at age 10-12 with flexible sigmoidoscopy annually for familial adenomatous polyposis 1, 5

Start colonoscopy 8-10 years after symptom onset, repeat every 1-3 years for inflammatory bowel disease (ulcerative colitis or Crohn's disease with colonic involvement) 1, 5

What Happens with Test Results

If FOBT is positive:

• Schedule colonoscopy within 60 days 3
• Do not repeat FOBT - any positive result requires colonoscopy 3
• Flexible sigmoidoscopy alone is inadequate as it misses proximal lesions 3

If FOBT is negative:

• Continue annual testing as scheduled 1
• A negative result does not rule out significant pathology in symptomatic patients 3
• For patients over 50 with persistent symptoms, colonoscopy may still be warranted regardless of negative FOBT 3

Alternative Screening Options

While FOBT is acceptable, other screening modalities include:

• Colonoscopy every 10 years (considered first-tier along with annual FIT) 1, 2
• Flexible sigmoidoscopy every 5 years (can be combined with annual FOBT) 1
• CT colonography every 5 years 1, 2
• FIT-DNA (multi-target stool DNA) every 3 years 1, 2

The choice between tests should consider that colonoscopy and FIT are ranked as first-tier options based on performance features and evidence 2

Common Pitfalls to Avoid

• Never use single-sample office FOBT - it has extremely poor sensitivity and should be abandoned 1, 3
• Do not use older low-sensitivity guaiac tests like Hemoccult II - upgrade to high-sensitivity versions or FIT 1
• Do not forget dietary and medication restrictions before testing, as they significantly affect accuracy 3
• Do not repeat FOBT if positive - proceed directly to colonoscopy 3
• Do not assume negative FOBT rules out cancer in symptomatic patients - clinical judgment determines need for colonoscopy 3