HOW ACCURATE ARE ENDOSCOPIC ESTIMATES OF SIZE

The accuracy of polyp size estimations in clinical studies is not know n. This study was designed to evaluate how well endoscopists can estim ate the size of objects at endoscopy. Observations were made by six at tending gastroenterologists, six gastroenterology fellows, and seven u ntrained medical residents. Ball bearings ranging in size from 3 mm to 19 mm were randomly inserted into a latex colon model, and size was e stimated while being viewed with a video colonoscope with and without the aid of an open biopsy forceps. Estimated size correlated well to a ctual size (R ranged from 0.78 to 0.93), although the mean estimates w ere consistently lower (13% to 29%) than the actual size for all group s, with and without forceps. The use of forceps did not improve the es timates. Exactly correct estimates occurred in 8%; errors of as much a s 110% were recorded. The 12 mm bearing was estimated to be less than 10 mm half of the time. We conclude that endoscopists frequently under estimate the size of objects viewed at the time of endoscopy. There wa s no difference in the performance of experienced gastroenterologists, fellows in training, or untrained residents. This study indicates tha t better methods of training and for determining size are needed. Rese arch that depends on endoscopic estimates of polyp size may be biased.