Which chemical substance is detected in a standard Guaiac-based Fecal Occult Blood Test (gFOBT)?
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Correct answer: Heme via pseudoperoxidase activity
The gFOBT relies on the pseudoperoxidase activity of the heme portion of hemoglobin. This reaction turns the guaiac-impregnated paper blue in the presence of hydrogen peroxide, though it can be affected by dietary intake of red meat or peroxidase-rich vegetables.
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