Colorectal cancer is a leading cause of cancer-related morbidity and mortality. CRC-related death can be prevented through fecal occult blood test screening. Because of economic and high sensitivity, fecal immunochemical test is recommended for screening population of CRC. The purpose of this study is to compare the accuracy of 4 different fecal occult blood testing in medium and high risk screening population in Chinese.

Colorectal cancer (CRC) is one of the most common cancer worldwide, and cause a huge number of cancer-associated mortality. CRC screening has been shown to be effective in reducing the incidence of, and mortality from, CRC. There are several recommended screening options for screening population of CRC, including colonoscopy and fecal occult blood testing (FOBT) .Colonoscopy has higher sensitivity and specificity than FOBT for detecting advanced colorectal neoplasia but also has several disadvantages, including higher cost and poorer compliance. Therefore, many patients prefer FOBT to colonoscopy. FOBT includes guaiac-based fecal occult blood test (gFOBT) and fecal immunochemical test (FIT). FIT includes quantitative FIT (qFIT) and qualitative FIT. qFIT can provide a value of concentration of hemoglobin in stool and are increasingly recommended for CRC. In China, the most common use FOBT is qualitative FIT and the comparison of quantitative and qualitative FIT is lack in screening population of CRC in Chinese. To add to the evidence on FIT performance characteristics for detection of CRC, the investigators design this research to compare qFIT with other 3 qualitative FOBT（two of them are colloidal gold qualitative FITs and one of them is chemical and immunologic combined detection）in medium and high risk screening population.

Inclusion Criteria:

• Adults 50-75 years old;
• Asia-Pacific Colorectal Screening score(APCS): medium or high risk.

Exclusion Criteria:

• APCS score: low risk;
• People with history of intestinal surgery;
• People with history of CRC;
• People with history of inflammatory bowel disease, ischemic enteritis, vascular malformation of intestine or other disease resulting in intestinal tract bleeding;
• People with symptoms including visible rectal bleeding, hematuria, severe and acute diarrhea and Bristol feces score 7th type;
• Pregnancy, lactation or menstrual phase;
• Severe congestive heart failure or other sever disease cause cannot tolerate colonoscopy.

Continuous participants intending to undergo colonoscopy and meet the inclusion and exclusion criteria from Qilu Hospital were enrolled.