Which lab test screens for hidden blood in stool samples?

• A. Hematocrit (Hct)
• B. Fecal occult blood test
• C. Hysterosalpingography
• D. Laparoscopy

Answer: (B)

Finding hidden blood in stool is done with a fecal occult blood test. It looks for microscopic blood in the stool that isn’t visible to the eye, which can come from sources like polyps, colorectal cancer, hemorrhoids, or ulcers in the digestive tract. Common approaches include guaiac-based tests or fecal immunochemical tests, which trigger a signal when blood (heme or hemoglobin) is present in the sample. This test is routinely used in colorectal cancer screening and to investigate symptoms such as anemia or GI bleeding.

Hematocrit measures the proportion of red blood cells in a blood sample, not stool. Hysterosalpingography is an imaging study of the uterus and fallopian tubes. Laparoscopy is a surgical procedure to view the abdominal cavity. None of these assess stool for occult blood.