Which definition best describes the guaiac test?

The guaiac test is primarily designed to detect hidden blood in stool, which can be an indicator of various medical conditions, such as gastrointestinal bleeding, ulcers, or colorectal cancer. The test utilizes a chemical reaction with guaiac resin that indicates the presence of hemoglobin—a component of blood—when it comes into contact with a stool sample. A positive result requires further investigation to discern the underlying cause of the bleeding.

Other options focus on different medical evaluations. A test for a urine infection would involve urinalysis or culture rather than a guaiac test. Evaluations for liver function typically include tests such as liver enzyme panels or bilirubin levels, while cholesterol levels are assessed through lipid panels. Therefore, the distinct purpose of the guaiac test in identifying internal bleeding distinguishes it as the correct answer.