BackgroundColorectal cancer (CRC) screening programs based on the fecal occult blood test (FOBT) reduce CRC mortality. We carried out an observational prospective study to determine the accuracy of immunochemical FOBTs for the detection of CRC in individuals at average risk for the disease.MethodsThis population-based study was performed between April 2015 and January 2016 in two gastroenterology referral centers in Southern Brazil. It included 1039 average-risk volunteers aged 50-75 years who were symptom-free for colonic disease. Participants underwent OC-Light immunochemical fecal occult blood test (i-FOBT, EIKEN chemical Co., Tokyo, Japan) as well as screening colonoscopy.ResultsNine hundred forty-eight (91.2%) of the 1039 participants completed and returned the i-FOBT (95% confidence interval [CI] 89.4-92.9). Among the 73 participants with a positive i-FOBT who underwent colonoscopy, advanced CRC was detected in 9 (12.3%). Two (2.7%) early CRCs, 7 (9.5%) high-grade dysplasia adenomas and 25 (34.2%) low-grade dysplasia adenomas were also diagnosed. Among the 243 negative i-FOBT cases who underwent colonoscopy, one (0.4%) advanced CRC and 91 (37.6%) low-grade dysplasia adenomas were detected. The detection rate of CRC considering the whole screened population (n=1039) was 1.05% (11/1039).ConclusionsThe i-FOBT test in the CRC screening programs in Brazil showed a high compliance and high detection rates for cancers and high-risk adenomas. The i-FOBT test is feasible for CRC screening in an average-risk population.