Cryptoblood refers to a test to confirm occult blood when small amounts of gastrointestinal bleeding cannot be demonstrated by visual and microscopic observation, and needs to be confirmed by chemical or immunological methods such as the occult blood test, whose positivity mainly reflects small amounts of bleeding in the gastrointestinal tract.
When there is a small amount of bleeding in the gastrointestinal tract, the color of the stool appearance may not change significantly and the red blood cells are destroyed by digestion and cannot be observed microscopically, so it is called occult blood. Occult blood can be confirmed by an occult blood test.
Fecal occult blood tests are often positive for gastrointestinal diseases such as peptic ulcers, damage to the gastric mucosa from drugs (e.g., aspirin, indomethacin, glucocorticoids, etc.), intestinal diseases (e.g., intestinal tuberculosis, Crohn’s disease, ulcerative colitis, colon polyps), hookworm disease, and gastrointestinal tumors (e.g., gastric cancer, colon cancer).
A change from a positive to a negative occult blood test can be a reliable indicator of complete cessation of bleeding from a peptic ulcer.
In the case of GI malignancies, the fecal occult blood test is usually consistently positive, so the occult blood test can be used as a screening indicator in the screening of GI malignancies.