Factors associated with false-positive and false-negative fecal immunochemical test results for colorectal cancer screening

Background: Certain subgroups have higher rates of false fecal immunochemical test (FIT) results, yet few studies have addressed this topic. Objective: To identify demographic factors associated with false-positive and false-negative FIT results in colorectal cancer screening. Design: Retrospective database review of prospectively collected data. Setting: A bowel cancer screening center in Hong Kong invited participants for colorectal cancer screening (2008-2012). Patients: Study participants who underwent both FIT and colonoscopy in the first year (n = 4482) and underwent colonoscopy after negative FIT results for 3 consecutive years (n = 857). Main Outcome Measurements: The diagnostic accuracy and predictive values of FIT according to participant characteristics. Results: The sensitivity, specificity, positive predictive values, and negative predictive values for advanced neoplasia were 33.1%, 91.9%, 19.0%, and 96.0%, respectively. Participants 66 to 70 years of age had higher sensitivity, whereas older age, smoking, and use of aspirin/nonsteroidal anti-inflammatory drugs were associated with lower specificity. The rates of false-positive and false-negative results were 8.1% and 66.9%, respectively. Older age (66-70 years; adjusted odds ratio [AOR] 1.95; 95% confidence interval [CI], 1.35-2.81; P < .001), smoking (AOR 1.68; 95% CI, 1.08-2.61; P =. 020), and the presence of polypoid adenoma (AOR 1.71; 95% CI, 1.14-2.57; P =. 009) were associated with false-positive results. Younger participants (AOR for elderly participants 0.31) and the use of aspirin/nonsteroidal anti-inflammatory drugs (AOR 4.44) in participants with 1 FIT with negative results and the absence of high-grade dysplasia (AOR for presence 0.41) were associated with false-negative results. Limitations: Self-referred participants who received one type of qualitative FIT. Conclusion: These findings could be used to target screening more toward those with a higher risk of false-negative results and those with a lower risk of false-positive results for earlier colonoscopy.