What does the term guaiac refer to in medical tests?

The term guaiac refers specifically to a substance used in medical tests to detect occult blood in feces. This is often utilized in stool tests, particularly the guaiac fecal occult blood test (FOBT), which screens for hidden (occult) blood that may indicate gastrointestinal bleeding, such as from polyps or colorectal cancer. The guaiac substance reacts with hemoglobin, a component of blood, producing a color change that signals the presence of blood in the stool, aiding in the early detection of potential health issues. The other choices do not accurately describe the function of guaiac; they pertain to distinct medical procedures that do not involve the detection of blood in feces.