Study and Comparison of Sensitivity Rates among Current Chemical Methods for Detecting Occult Blood in Stool

Any abnormality in stool compounds can be an indication of colon disfunction or diseases. Occult bleeding which is determined by means of occult blood test(peroxidase activity) is the most valuable diagnostic test for primary stage of colorectal neoplasia which can be fully prevented. Considering dietary precautions, foods such as red meat, fish, vegetables, vitamin C and iron containing anti-inflammatory non-sterodial drugs should not be consumed at least three days prior to doing the test. Common techniques for conducting the occult blood test are the Meyer, Guaiac, O-Tolidine, Pyramidine alcohol methods and a few commercial kits such as Hematape. The principle behind all of these methods are the oxidation of the chromogen reagents, by O2 released of H2O2 due to the peroxidase activity present in RBC hemoglobin with the subsequent induction of color. In order to determine the sensitivity of each of these methods, blood was added in different amounts to human stool samples. The Meyer method was found to be the most sensitive way of conducting the occult blood test and it can detect pathologic bleeding of GI tract within the range of 5-10ml of bleeding per day. The other methods, in terms of their relative sensitivity were: the Guaiac method, O-Tolidine method, Pyramidine alcohol and Hematape, respectively.Hematape kit showed the least sensitivity and it can detect bleeding less than 81.5ml per day. The main purpose of conducting this study was to determine conventional occult blood tests(OB tests) and choose the best one in order to be presented and introduced to clinical pathology laboratories in all over the country.