Can colon cancer be diagnosed on a fecal occult blood test?

No: Gi bleeding can come from many causes, but the most serious is cancer. That is why it needs to be evaluated with endoscopy including biopsy of anything suspicious.

FOBT is screen: Fobt is designed to test for blood in stool. Blood in stool may be due to any bleeding in the GI tract from the gums to the anus; and there are false positives also. If fobt is positive, colonoscopy is generally recommended to look of colon cancer. Fobt per se is not a diagnostic test for cancer, just blood in stool.

No: Fecal occult blood testing looks for unseen blood in the stool. One should not have blood in the stool. If the fecal occult blood test is positive, the next steps are to determine why. One reason could be colon cancer and this can be the most dangerous reason why fecal occult blood occurs. There are however, other reasons with benign causes.

The circum-: Stantial evidence of blood can have causes beside cancer, i.e., polyp, divertic, bleeding ulcer from upper tract, even a bloody nose, but the finding of occult blood warrants investigation: colonoscopy or rarely today, barium enema.