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Guaiac-based fecal occult blood tests (FOBTs) are nonspecific and insensitive. Researchers with support from the maker of a quantitative immunochemical FOBT specific for human hemoglobin tested its performance in 1000 ambulatory adults undergoing elective colonoscopy. Some patients were asymptomatic, some were at high risk for cancer, and some were symptomatic.
At colonoscopy, cancer was detected in 17 patients, and advanced polyps in 74. Fecal hemoglobin concentrations were significantly higher in these patients than in others. A fecal hemoglobin threshold of 75 ng/dL (as measured in 3 samples) was used to define an abnormal result; at this level, the immunochemical FOBT had a sensitivity of 67% and specificity of 91% for advanced neoplasia…