Comparative evaluation of immunochemical fecal occult blood tests for colorectal adenoma detection

Abstract

Background: Different immunochemical fecal occult blood tests (FOBTs) have been proposed for noninvasive colorectal cancer screening. Large-scale, colonoscopy-based screening studies that allow evaluation of these tests for the detection of precursor lesions are scarce.

Objective: To determine and compare performance characteristics of 6 qualitative immunochemical FOBTs for identifying colorectal adenomas among adults who attended screening colonoscopy examinations.

Design: Prospective screening study from January 2006 to December 2007.

Setting: 20 gastroenterology practices in Germany that did screening colonoscopy.

Patients: 1319 participants at average risk for colorectal neoplasia who were undergoing screening colonoscopy (mean age, 63 years; 50% men).

Measurements: 6 different qualitative immunochemical FOBTs were done with stool samples collected before bowel preparation for colonoscopy. Performance characteristics (sensitivity, specificity, predictive values, and likelihood ratios) of tests were measured by comparing test results with findings on colonoscopy. Technicians who read the tests were blinded to colonoscopy results, and colonoscopists were blinded to FOBT results.

Results: Overall, 405 participants (31%) had an adenoma and 130 participants (10%) had an advanced adenoma. Performance characteristics varied widely among tests. For the 2 best-performing tests (immoCARE-C [CAREdiagnostica, Voerde, Germany] and FOB advanced [ulti med, Ahrensburg, Germany]), the sensitivity for detection of advanced adenomas was 25% (95% CI, 18% to 34%) and 27% (CI, 20% to 35%), respectively; specificity was 97% (CI, 95% to 98%) and 93% (CI, 91% to 95%); and the positive likelihood ratio was 3.5 (CI, 2.2 to 5.4) and 2.5 (CI, 1.9 to 3.5).

Limitation: The study differed from real-life conditions in that stool samples were not directly dissolved in a buffer-filled vial; instead, a small container was used and stool was frozen before testing.

Conclusion: Qualitative immunochemical FOBTs could be an option for future colorectal cancer screening because they showed better performance characteristics for precursor lesions than guaiac-based FOBTs and are practical for mass screening. However, given the large differences in diagnostic performance among tests, careful evaluation of the different test variants is important.

Funding: The German Research Foundation (Deutsche Forschungsgemeinschaft) within the framework of a PhD program (Graduiertenkolleg 793).