A comparative study of chemical and immunological method of fecal occult blood test in the diagnosis of occult lower gastrointestinal bleeding.

Fecal occult blood test is the most widely used screening test for diagnosis of gastrointestinal bleeding disorders specially colorectal carcinoma. Among the various methods of fecal occult blood tests, chemical method is being used commonly, but the method has some drawbacks like low participation rate, high false positive rate, low sensitivity etc. To overcome these short comings, newer immunological method was introduced. This study evaluated the role of immunological method of fecal blood test in the diagnosis of occult lower GIT bleeding. Stool samples from two hundred patients were examined by both chemical and immunological method. The patients who were positive by any or both methods of occult blood test, were advised for colonoscopy. During colonoscopy tissues were taken for histopathology which was the gold standard of this study. Among 110 OBT positive patients pathological lesions were detected in 65 patients by colonoscopy and histopathology. The diseases detected by colonoscopy and histopathology 18 colorectal polyp, 8 colorectal cancer, 24 ulcerative lesions and 5 inflammatory bowel disease etc. Regarding comparative analysis of chemical and immunological method, the higher sensitivity (95.4% vs. 49.2%), specificity (44.4% vs. 37.8%), accuracy (74.5% vs. 44.5%), PPV (71.3% vs. 53.3%) and NPV (87% vs. 34%) of immunological method than chemical method was observed. Thus immunological method of fecal occult blood test was appeared to be a better alternative to conventional chemical method of fecal occult blood test in the diagnosis of occult lower GIT bleeding.