Comparative Effectiveness of Fecal Immunochemical Tests with Optical Colonoscopy

Colorectal cancer (CRC) is the third most common cancer and the third leading cause of cancer death in both men and women in the U.S., with nearly 50,000 deaths each year. Since CRC develops over a number of years from precursor lesions called polyps, it is largely detectable and preventable in early stages. As these polyps become larger, they, like most CRCs, tend to bleed, which is the rationale for the use of fecal occult blood tests (FOBTs) to detect both polyps and cancers early, while they are curable. However, early screening and detection is much less common than it could be, with about 43% of eligible individuals unscreened. Fecal immunochemical tests (FITs) are a type of FOBT that can be a sensitive, specific, and lowcost alternative to colonoscopy for CRC screening. Modeling studies have shown that for population screening, a strategy of annual FIT testing from age of 50 to 75 years results in an equal number of life-years gained as compared with colonoscopy every 10 years. However, about 90% of screening in the U.S. is done with colonoscopy, the most expensive and invasive screening test. FITs are far less costly and largely replacing the guaiac test in CRC screening programs internationally, where only individuals with positive results are referred for a colonoscopy. Studies done on FITs in other countries often used FITs not available in the U.S. or studied high-risk populations; thus, results are not applicable in the U.S. It is critical to determine the FIT(s) with the best test characteristics in order to implement successful FIT-based screening programs in this country. It is estimated that 24 million more individuals will need to be screened by 2018 to reach the “80% by 2018” goal set by the National Colorectal Cancer Roundtable. To address this knowledge gap, we propose to compare the test characteristics of three CLIA-waived FITs and two automated FITs, using colonoscopy as the gold standard. The rationale for this proposed study is that, for almost all of the FITs currently marketed in the U.S., there is no evidence of the accuracy claimed. Our aims are: Aim 1: To assess the diagnostic accuracy for advanced colorectal neoplasms of three of the most commonly used CLIA-waived FITs and two automated FITs, using colonoscopy as the gold standard. Aim 2: To evaluate the diagnostic accuracy of two quantitative FITs using receiver operating characteristic (ROC) analysis. Aim 3: To assess factors associated with false positive and false negative FIT results for each device. These findings will provide essential information about FITs with the best test characteristics for future expanded use of FIT, critically important to achieving our long-term goal of reducing morbidity and mortality from CRC. FITs are more acceptable to patients, will allow higher screening rates, and will reduce costs as compared with a screening strategy based on colonoscopy as the primary initial screening method.