Which test detects occult blood in the stool?

• A. Pancreatitis
• B. Paracentesis
• C. Ileostomy
• D. Stool guaiac test

Answer: (D)

Detecting occult blood in the stool means finding hidden bleeding somewhere in the gastrointestinal tract. The stool guaiac test does this by using guaiac-impregnated paper and hydrogen peroxide. If blood is present, the heme in the blood acts like a peroxidase and catalyzes a reaction that turns the paper blue. A positive result suggests occult GI bleeding and can be used in screening for colorectal cancer or evaluating unexplained iron-deficiency anemia. This test is not about pancreatic function, fluid in the abdomen, or surgical stool collection—conditions like pancreatitis, paracentesis, or an ileostomy involve different processes. Also, substances in the diet or certain medications can affect the guaiac reaction, leading to false positives or negatives, so proper preparation and follow-up testing are important.