Occult blood tests.
D003110:Colonic Neoplasms / Q000175:diagnosis; D003951:Diagnostic Errors; D006801:Humans; D007124:Immunoenzyme Techniques; D007504:Iron Radioisotopes; D008551:Melena / Q000175:diagnosis; D009780:Occult Blood; D012004:Rectal Neoplasms / Q000175:diagnosis
D007504:Iron Radioisotopes