EVALUATION OF TESTS FOR OCCULT BLOOD IN THE FECES: SIGNIFICANCE OF GUAIAC AND ORTHOTOLIDINE TESTS AFTER INGESTION OF IRON

The presence of occult blood in the feces is of great clinical importance both as an early finding with undetected gastrointestinal neoplasm and as an indication of an important complication of already known gastrointestinal disease. Patients in whom it is most necessary to detect small amounts of blood in the feces are often those with hypochromic anemia, and they are often taking therapeutic amounts of iron when tested. It is widely believed that the ingestion of iron will cause a positive test with guaiac (Bell, 1 Burger, 2 Hoerr and associates 3 ). Textbooks of clinical pathology (Ham, 4 Gradwohl 5 ) are noncommittal on the question, and the published articles are few and conflicting. It would be of clinical worth then if the reliability of the guaiac test done on the stool of a patient taking a normal diet with and without iron ingestion could be determined. The guaiac test was