Specimen Stool Volume 5 g Container Collection card or sterile leakproof container with screw-cap Storage Instructions Maintain specimen at room temperature. Antacids may cause false-negative guaiac tests.
Therapeutic iron causes false-positives with guaiac tests in over half of healthy subjects.
Most methods lack sensitivity to small amounts of blood and might fail to detect slow rates of blood loss. When occult GI bleeding is suspected, at least three samples, from separate bowel movements, should be submitted. Many substances and conditions interfere with guaiac tests. False-positive results may be caused by excessive dietary intake of vegetable peroxidases, especially horseradish. Guaiac tests present a number of other problems.