Timing and Risk Factors for a Positive Fecal Immunochemical Test in Subsequent Screening for Colorectal Neoplasms.

ABSTRACT

BACKGROUND: Following a negative test, the performance of fecal immunochemical testing in the subsequent screening round is rarely reported. It is crucial to allocate resources to participants who are more likely to test positive subsequently following an initial negative result. OBJECTIVE: To identify risk factors associated with a positive result in subsequent screening. METHODS: Dataset was composed of consecutive participants who voluntarily underwent fecal tests and colonoscopy in a routine medical examination at the National Taiwan University Hospital between January 2007 and December 2011. Risk factor assessment of positive fecal test in subsequent screening was performed by using the Cox proportional hazards models. RESULTS: Our cohort consisted of 3783 participants during a 5-year period. In three rounds of subsequent testing, 3783, 1537, and 624 participants underwent fecal tests, respectively; 5.7%, 5.1%, and 3.9% tested positive, respectively, and the positive predictive values were 40.2%, 20.3%, and 20.8%, respectively. Age ≥60 years (adjusted hazard ratio 1.53, 95% CI 1.21-1.93) and male gender (1.32, 95% CI 1.02-1.69) were risk factors; however, an interaction between age and gender was noted. Men had higher risk than women when they were <60 years of age (p = 0.002), while this difference was no longer observed when ≥60 years of age (p = 0.74). The optimal interval of screening timing for participant with baseline negative fecal test was 2 years. CONCLUSIONS: Following a negative test, older age and male gender are risk factors for a positive result in the subsequent rounds while the gender difference diminishes with age. Biennial screening is sufficient following a negative fecal test.