Individual tests

The fecal occult blood test (FOBT) checks stool samples for hidden (occult) blood. Occult blood in the stool may indicate colon cancer or polyps in the colon or rectum — though not all cancers or polyps bleed. If blood is detected through a fecal occult blood test, additional tests such as a colonoscopy may help determine the source of the bleeding. The fecal occult blood test can only detect the presence or absence of blood — it can't determine what's causing the bleeding.
Interleukin-6 (IL-6) is a protein that helps regulate immune responses, which makes the IL-6 test potentially useful as a marker of immune system activation. This test may be used to help evaluate a person who has a condition associated with inflammation, such as lupus, rheumatoid arthritis, or with infections like sepsis.