Colorectal Cancer Screening

Test Performance

• Immunochemical fecal occult blood tests (iFOBTs) have superior sensitivity and specificity compared to guaiac-based tests (gFOBTs), with sensitivity for colorectal cancer ranging from 50-75% (95% CI: 0.09-1.0) and specificity ranging from 96-98% (95% CI: 0.95-0.99), as recommended by the American College of Physicians 1
• The OC-Sensor family of iFOBTs has a sensitivity of 74% (95% CI: 0.64-0.83) and specificity of 94% (95% CI: 0.93-0.96) for colorectal cancer 1
• High-sensitivity gFOBTs perform better than standard gFOBTs, according to the National Comprehensive Cancer Network 2
• The sensitivity for advanced adenomas is much lower, ranging from 6-17% (95% CI: 0.02-0.23) 1
• The highest sensitivity for colorectal cancer using iFOBTs is 93% (95% CI: 0.87-1.0), but this comes with a lower specificity of 84% (95% CI: 0.84-0.86) 1
• Meta-analysis of 19 studies shows pooled sensitivity of 79% (95% CI: 69-86%) for iFOBT in colorectal cancer detection, with a pooled specificity of 94% (95% CI: 92-95%) 3

Testing Frequency and Follow-up

• The National Comprehensive Cancer Network recommends annual testing due to the limited sensitivity of a single test, especially for early-stage cancers and advanced adenomas 2
• Any positive FOBT result must be followed by diagnostic colonoscopy, as recommended by the National Comprehensive Cancer Network 2
• Repeat testing at regular intervals (annually) is required for iFOBT screening 4, 5

Test Threshold and Performance

• The sensitivity for advanced adenomas can be as high as 43% (95% CI: 0.40-0.46) using iFOBTs 1
• The sensitivity for advanced adenomas using the OC-Sensor family is 23% (95% CI: 0.20-0.25) 1
• Cut-off threshold: Sensitivity can be adjusted by altering the hemoglobin threshold for a positive result, with lower thresholds increasing sensitivity but decreasing specificity 3
• Number of samples: Two-sample testing appears to provide optimal balance between sensitivity and cost-effectiveness, while single-sample testing may miss intermittent bleeding 4
• Brand variations: Different commercial iFOBT brands show varying performance, with OC-Sensor and OC FIT CHEK demonstrating consistently good performance 3

Limitations and Pitfalls

• iFOBT is less sensitive for early-stage cancers and advanced adenomas 3
• Cannot detect non-bleeding lesions 4
• Inadequate follow-up, single in-office testing, delayed colonoscopy, and misinterpreting negative results are common pitfalls in iFOBT screening 5

Comparison of Test Types

3, 4, 6

• The American Cancer Society recommends iFOBT as a screening option for colorectal cancer, with higher sensitivity for cancer detection compared to guaiac-based tests 4
• iFOBT demonstrates superior performance compared to traditional gFOBT, with higher sensitivity for cancer detection and excellent specificity, and key advantages include higher sensitivity for cancer detection, no dietary restrictions required, better patient compliance, quantitative results possible with some brands, and automated processing available 3, 4, 6, 2