Zhao S, et al. - Researchers comprehensively evaluated the adenoma miss rate (AMR) and advanced AMR (AAMR) and explored associated factors via performing meta-regression analyses. For this systematic review and meta-analysis, PubMed, Web of Science, and Ovid EMBASE databases were searched for studies published through April 2018 on tandem colonoscopies, with AMR and AAMR as the primary outcomes. Investigators found high miss rates for proximal advanced adenomas, serrated polyps, flat adenomas, and high colorectal cancer risk in patients. They suggested that miss rates could be reduced by adequate bowel preparation and auxiliary techniques. Findings suggested an independent association of the adenoma detection rate (ADR), adenomas per index colonoscopy, and adenomas per positive index colonoscopy (APPC) with AMR. On the other hand, APPC was the only factor independently linked to AAMR. More frequently than previously thought, adenomas and advanced adenomas are missed (based on AMR and AAMR). Besides ADR, if validated in additional studies, APPC should be considered an indicator of colonoscopy quality.