Occult blood tests.
D000328:Adult; D003110:Colonic Neoplasms / Q000175:diagnosis; D005069:Evaluation Studies as Topic; D005188:False Negative Reactions; D006801:Humans; D007417:Intestinal Polyps / Q000175:diagnosis; D008551:Melena / Q000175:diagnosis*; D008875:Middle Aged; D009780:Occult Blood; D012004:Rectal Neoplasms / Q000175:diagnosis