Is It Necessary to Repeat Fecal Occult Blood Tests with Borderline Results for Colorectal Cancer Screening?

The fecal immunochemical test (FIT) is the initial non-invasive investigation of choice for population-based colorectal cancer (CRC) screening. We evaluated the positivity rate in repeated tests using the same fecal specimen that showed borderline results in the FIT. A total of 6,465 patients were tested with the FIT in a tertiary-care hospital from July to December 2016. FIT was done using OC-Sensor PLEDIA (Eiken Chemical Co., Tokyo, Japan). Among 6,465 patients, 364 (5.6%) patients showed a positive FIT result of over 20 μg Hb/g feces. A total of 112 (1.7%) patients showed borderline scores of 10.2-20 μg Hb/g feces, and 5,989 (92.6%) patients showed negative results of less than 10 μg Hb/g feces. Among the 101 repeat-tested patients, 19 (18.8%) of the patients' scores converted to levels above the positive cut-off threshold. Repeated results of 19 patients showed score elevations from 20.2 to 68 μg Hb/g feces. These results suggest that it is most important to analyze properly prepared samples, even if only once. Therefore, the laboratory staff should ensure the proper preparation of stool specimens for FIT. Laboratory directors should choose the best cut-off value for detecting CRC at their respective institutions.