INTRODUCTION: Although the 9-minute mean withdrawal time (m-WT) is often reported to be associated with the optimal adenoma detection rate (ADR), no randomized trials of screening colonoscopy have confirmed the impact of a 9-minute m-WT on adenoma miss rate (AMR) and ADR. METHODS:A multicenter tandem trial was conducted in 11 centers. Seven hundred thirty-three asymptomatic participants were randomized to receive segmental tandem screening colonoscopy with a 9-minute withdrawal, followed by a 6-minute withdrawal (9-minute-first group, 9MF, n 5 366) or vice versa (6-minute-first group, 6MF, n 5 367). The primary outcome was the lesion-level AMR. RESULTS:The intention-to-treat analysis revealed that 9MF significantly reduced the lesion-level (14.5% vs 36.6%, P < 0.001) and participant-level AMR (10.9% vs 25.9%, P < 0.001), advanced adenoma miss rate (AAMR, 5.3% vs 46.9%, P 5 0.002), multiple adenomas miss rate (20.7% vs 56.5%, P 5 0.01), and high-risk adenomas miss rate (14.6% vs 39.5%, P 5 0.01) of 6MF without compromising detection efficiency (P 5 0.79). In addition, a lower false-negative rate for adenomas (P 5 0.002) and high-risk adenomas (P < 0.05), and a lower rate of shortening surveillance schedule (P < 0.001) were also found in 9MF, accompanying with an improved ADR in the 9-minute vs 6-minute m-WT (42.3% vs 33.5%, P 5 0.02). The independent inverse association between m-WT and AMR remained significant even after adjusting ADR, and meanwhile, 9-minute m-WT was identified as an independent protector for AMR and AAMR.

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