RT Journal Article SR Electronic T1 Designs of colonoscopic adenoma detection trials: more positive results with tandem than with parallel studies - an analysis of studies on imaging techniques and mechanical devices JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP gutjnl-2020-320984 DO 10.1136/gutjnl-2020-320984 A1 Katharina Zimmermann-Fraedrich A1 Heiko Pohl A1 Thomas Rösch A1 Douglas K Rex A1 Cesare Hassan A1 Evelien Dekker A1 Michal Filip Kaminski A1 Michael Bretthauer A1 Jocelyn de Heer A1 Yuki Werner A1 Guido Schachschal A1 Stefan Groth YR 2020 UL http://gut.bmj.com/content/early/2020/05/14/gutjnl-2020-320984.abstract AB Background and aims Adenoma detection rate (ADR) has been shown to correlate with interval cancers after screening colonoscopy and is commonly used as surrogate parameter for its outcome quality. ADR improvements by various techniques have been studied in randomised trials using either parallel or tandem methodololgy.Methods A systematic literature search was done on randomised trials (full papers, English language) on tandem or parallel studies using either adenoma miss rates (AMR) or ADR as main outcome to test different novel technologies on imaging (new endoscope generation, narrow band imaging, iScan, Fujinon intelligent chromoendoscopy/blue laser imaging and wide angle scopes) and mechanical devices (transparent caps, endocuff, endorings and balloons). Available meta analyses were also screened for randomised studies.Results Overall, 24 randomised tandem trials with AMR (variable definitions and methodology) and 42 parallel studies using ADR (homogeneous methodology) as primary outcome were included. Significant differences in favour of the new method were found in 66.7% of tandem studies (8222 patients) but in only 23.8% of parallel studies (28 059 patients), with higher rates of positive studies for mechanical devices than for imaging methods. In a random-effects model, small absolute risk differences were found, but these were double in magnitude for tandem as compared with parallel studies (imaging: tandem 0.04 (0.01, 0.07), parallel 0.02 (0.00, 0.04); mechanical devices: tandem 0.08 (0.00, 0.15), parallel 0.04 (0.01, 0.07)). Nevertheless, 94.2% of missed adenomas in the tandem studies were small (<1 cm) and/or non-advanced.Conclusions A tandem study is more likely to yield positive results than a simple parallel trial; this may be due to the use of different parameters, variable definitions and methodology, and perhaps also a higher likelihood of bias. Therefore, we suggest to accept positive results of tandem studies only if accompanied by positive results from parallel trials.