Abstract
The immunological fecal occult blood test has been recognized as an effective tool for detecting colorectal cancers, but one of its shortcomings is that false negative findings are inevitable. We examined the false negative cases among the 212 cases of colorectal cancer detected among the 177,887 examinees for whom an immunological fecal occult blood test was carried out at our institute. False negative cases were found to account for 36.3% of the colorectal cancer cases, and 25% of those were advanced cancers. The fecal occult blood quantitative values were significantly lower in the false negative group (FN group) compared to the group that had been positive in the previous test (PP group) and the group that had been found positive in the first test (FP group). Considering that 73.9% of the cases were type 0, 69.2% had lesions 2 cm or less in size and the rate of intramucosal cancer was 54.5%, the false negative findings seemed to be related to the fact that the lesions were detected at early stages in more cases of the FN group compared to the other two groups. The rate of Dukes A in the FN group was about 80%, and endoscopic treatment was selected for 61.3% of the cases. Half of the advanced cancers in the FN group, however, were detected in the right colon, which reconfirmed the shortcoming of the immunological fecal occult blood test in detecting lesions in the right colon. The high rate of false negative results for colon cancer detection is a problem with this test, especially for the detection of cancer in the right colon. It seems essential for colorectal cancer mass screenings that health care professionals have a good understanding of the immunological fecal occult blood test, endeavor to increase its rate of application, and encourage people to have the test annually.
