Background and purpose: Shanghai provides free colorectal cancer screening services to eligible residents. This study aimed to analyze immunochemical fecal occult blood test results in colorectal cancer screening to assess the effectiveness of twice fecal occult blood test

and to provide the evidence for community-based screening programs. Methods: Shanghai residents aged 50-74 years were target population. Twice immunochemical fecal occult blood test and risk assessment were used for initial screening

along with colonoscopy for individuals whose initial results were positive. Results: During the screening

809 528 participants completed immunochemical fecal occult blood test twice

and 104 953 people’s test results were positive. There were 47 421 people whose initial results were positive

and the positive rate was 5.9%. There were 36 462 people who got positive results in the second test

and the positive rate was 4.5%. Another 21 070 people got positive results in both tests

and the positive rate was 2.6%. Among the individuals with positive immunochemical fecal occult blood test

49 339 people underwent colonoscopy

and the overall colonoscopy compliance was 47.0%. The participation rate of colonoscopy was significantly higher in participants who had double positive results than in the participants with single positive result. One thousand two hundred cases (79.5%) of colorectal cancer were diagnosed and 3 777 cases (68.1%) of precancerous lesions were detected by only one fecal occult blood test. Three hundred and ten cases (20.5%) of colorectal cancer were diagnosed and 1 767 cases (31.9%) of precancerous lesions were detected by an additional fecal occult blood test. Conclusion: Compared with the only one immunochemical fecal occult blood test

the twice tests were more effective. The compliance of colonoscopy was improved among participants with double positive results

and the detective rates of colorectal cancer and precancerous lesions were increased. To improve the screening efficiency

twice or more immunochemical fecal occult blood test should be carried out in the community-based colorectal cancer screening.