We aim to evaluate the effect of aspirin on fecal immunochemical test (FIT) performance for advanced colorectal neoplasia (ACRN) including advanced adenoma (AA) and colorectal cancer (CRC).
A multicenter study involved 4887 individuals who were asked to complete a quantitative FIT and subsequent colonoscopy. Aspirin users and nonusers were matched for age and sex. The primary outcome was the positive predictive value (PPV) of FIT compared between users and matched nonusers. Univariable and multivariable logistic regression analyses were also conducted in the entire cohort and expressed as odds ratio (OR) with 95% confidence interval (CI).
For AA, the PPV of FIT was 25.30% in users vs. 14.71% in nonusers (p = 0.005), and the detection rate was 8.28% in users vs. 4.44% in nonusers (p = 0.003). The multivariable OR after adjusting age and sex was 1.52 (95% CI, 1.02-2.22, p = 0.036) for PPV and 1.41 (95% CI, 0.99-1.99, p = 0.052) for the detection rate compared between users and nonusers. Aspirin did not affect the sensitivity and specificity of FIT for AA. Additionally, no significant difference in FIT performance for ACRN and CRC was observed.
The use of aspirin increased detection rate and PPV of FIT for AA, without impact on FIT performance for ACRN and CRC. Given the risk of cardiovascular events and influence on participation rate of FIT screening, aspirin withdrawal before FIT is unnecessary.

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