Background: Flexible sigmoidoscopy and fecal immunochemical tests are established diagnostic tests for colorectal cancer (CRC) screening and less invasive, less expensive, and easier to conduct than colonoscopy. However, little is known about their joint diagnostic performance compared with colonoscopy. We aimed to assess the expected diagnostic performance of joint use of flexible sigmoidoscopy and fecal immunochemical test.
Methods: We assessed the overall and site-specific prevalences of colorectal neoplasms and the overall sensitivity, specificity, area under the receiver operating characteristics curve of a quantitative fecal immunochemical test (FOB Gold, Sentinel Diagnostics, Milano, Italy) among 3,466 participants in screening colonoscopy in Germany. Results were used to model the expected diagnostic performance of joint use of flexible sigmoidoscopy and fecal immunochemical testing.
Results: CRC and advanced adenomas were found in 29 (1%) and 354 (10%) participants, respectively. The area under the curve of fecal immunochemical testing for these outcomes could be raised from 96% to 100% and from 70% to 89%, respectively, by combining it with flexible sigmoidoscopy. At 90% specificity, sensitivity of fecal immunochemical testing would increase from 97% to 100% for CRC and from 40% to 79% for advanced adenomas.
Conclusions: Combining flexible sigmoidoscopy and fecal immunochemical testing might strongly enhance diagnostic performance of each single test to a level close to the diagnostic performance of screening colonoscopy while avoiding many unnecessary colonoscopies.