Use of Acetylsalicylic Acid (ASA) for Enhanced Early Detection of Colorectal Neoplasms

Interventions: Group 1: Volunteers in arm 1 receive a single oral dose of acetylsalicylic acid (ASA) 300 mg, in order to evaluate the diagnostic potential of two immunochemical Fecal Occult Blood Tests (iFOBTs) for detecting advanced colorectal neoplasms.
Only volunteers with a planned (study-independent) colonoscopy (6 days to 3 month after ASA) are included.
Group 2: Volunteers in arm 2 receive a single oral dose of a placebo. Other procedures are identical to arm 1.
Primary outcome(s): To evaluate diagnostic performance (sensitivity, specificity, positive and negative predictive values, likelihood ratios, area under the curve) of 2 imunochemical Fecal Occult Blood Tests for detecting advanced colorectal neoplasms after a single dose of aspirin as compared to application of the tests without prior use of aspirin.
Study Design: Allocation: Randomized controlled study; Masking: Blinded (masking used); Control: placebo; Assignment: parallel; Study design purpose: screening