A healthy 48-year-old physician with no family history of cancer and who strictly adheres to a high protein, high fiber diet, exercises five times per week for 50 minutes, and takes vitamin C supplements daily performs a fecal occult blood test (FOBT) on herself and tests positive. Should she have any further colon screening?A. No, vitamin C can produce a false-positive result
Fecal occult blood test (FOBT) has been a nonspecific test for peroxidase contained in hemoglobin; consequently, occult bleeding from any gastrointestinal source will produce a positive result. Similarly, many foods (red meat, some fruits and vegetables, and vitamin C) will produce a false-positive result. Any positive FOBT mandates further investigation, usually by colonoscopy.