American Journal of Gastroenterology ISSN 0002-9270 C  2006 by Am. Coll. of Gastroenterology doi: 10.1111/j.1572-0241.2006.00390.x Published by Blackwell Publishing Polyp Miss Rate Determined by Tandem Colonoscopy: A Systematic Review CME Jeroen C. van Rijn, M.D., 1 Johannes B. Reitsma, M.D., Ph.D., 1 Jaap Stoker, M.D., Ph.D., 2 Patrick M. Bossuyt, Ph.D., 1 Sander J. van Deventer, M.D., Ph.D., 3 and Evelien Dekker, M.D., Ph.D. 3 1 Departments of Clinical Epidemiology & Biostatistics; 2 Radiology; and 3 Gastroenterology, Academic Medical Center (University of Amsterdam), Amsterdam, The Netherlands BACKGROUND Colonoscopy is the best available method to detect and remove colonic polyps and therefore serves AND AIMS: as the gold standard for less invasive tests such as virtual colonoscopy. Although gastroenterologists agree that colonoscopy is not infallible, there is no clarity on the numbers and rates of missed polyps. The purpose of this systematic review was to obtain summary estimates of the polyp miss rate as determined by tandem colonoscopy. METHODS: An extensive search was performed within PUBMED, EMBASE, and the Cochrane Library databases to identify studies in which patients had undergone two same-day colonoscopies with polypectomy. Random effects models based on the binomial distribution were used to calculate pooled estimates of miss rates. RESULTS: Six studies with a total of 465 patients could be included. The pooled miss rate for polyps of any size was 22% (95% CI: 19–26%; 370/1,650 polyps). Adenoma miss rate by size was, respectively, 2.1% (95% CI: 0.3–7.3%; 2/96 adenomas ≥10 mm), 13% (95% CI: 8.0–18%; 16/124 adenomas 5–10 mm), and 26% (95% CI: 27–35%; 151/587 adenomas 1–5 mm). Three studies reported data on nonadenomatous polyps: zero of eight nonadenomatous polyps ≥10 mm were missed (0%; 95% CI: 0–36.9%) and 83 of 384 nonadenomatous polyps <10 mm were missed (22%; 95% CI: 18–26%). CONCLUSIONS: Colonoscopy rarely misses polyps ≥10 mm, but the miss rate increases significantly in smaller sized polyps. The available evidence is based on a small number of studies with heterogeneous study designs and inclusion criteria. (Am J Gastroenterol 2006;101:343–350) INTRODUCTION Colorectal cancer is the second leading cause of cancer death in the United States (1). It has been shown that a significant reduction of the incidence of colorectal cancer can be achieved by removing adenomatous polyps before their potential progress to adenocarcinomas (2). Currently, colonoscopy is the best available method to detect and re- move colonic polyps and can therefore be considered as the gold standard for this purpose (3, 4). However, colonoscopy is not infallible and although most gastroenterologists are aware that polyps can be missed during colonoscopy, numbers and rates remain uncertain. Furthermore, as population-based studies on colorectal cancer screening are progressing, it is conceivable that in the near future many western countries adopt colorectal can- cer screening of all individuals aged 50 or above, leading to a vast increase in the number of colonoscopic examinations. Within the debate on mass screening for colorectal cancer, a Evelien Dekker is a fellow of the Dutch Cancer Foundation. To access a continuing medical education exam for this article, please visit www.acg. gi.org/journalcme. quantification of polyp miss rate is essential for future cost- benefit analyses. Besides its use in clinical practice or screening, colonoscopy also serves as the reference standard in many studies on the evaluation of less invasive tests such as virtual colonoscopy or fecal tests. Misclassification of the reference standard, however, can influence the perceived accuracy of the test under evaluation (5). Without accurate estimates of colonoscopic miss rates, the impact on the test accuracy can- not be deduced. The most reliable method to investigate polyp miss rate is by “tandem” or “back-to-back” colonoscopy, a method in which two same-day colonoscopies, both with polypectomy, are performed within each patient. In such studies, the miss rate is usually expressed as the number of polyps detected only during the second colonoscopy relative to the number of polyps found during both examinations. The purpose of this systematic review was to appraise the evidence from all available studies on tandem colonoscopy and to obtain summary estimates of the colonoscopic polyp miss rate. We also investigated possible sources of hetero- geneity in miss rate within and between studies. 343