What is the sensitivity and specificity of guaiac testing for fecal blood?
- The sensitivity of guaiac testing depends on the specific brand used. Several guaiac reagents are marketed. The most sensitive brand is the Hemoccult II-SENSA test.
- The sensitivity also depends on the lesion to be detected. It is not a good test for detecting colonic adenomas because adenomas infrequently bleed.
- It is moderately (up to 80%) sensitive at detecting colon cancer when performed on 3 consecutive days to account for intermittent bleeding from colon cancer.
- The specificity of guaiac testing is only approximately 20% to 30% for detecting significant colonic lesions.
- The yield of colonoscopy performed for a guaiac-positive test is colon cancer in 3% to 4% of patients and colonic adenomas in 15% to 20% of patients (or higher in older adult patients).
