title: Polyp measurement reliability, accuracy, and discrepancy: optical colonoscopy versus CT colonography with pig colonic specimens.
abstract: OBJECTIVE
  To prospectively evaluate the reliability and accuracy of optical colonoscopy and computed tomographic (CT) colonography in polyp measurement, by using direct measurement as the reference standard, and to understand the basis for measurement discrepancy between both modalities.
  
  
  METHODS
  Eighty-six simulated polyps that ranged from 3 to 15 mm were constructed by using pig colons obtained from an abattoir. Approval of the animal care and use committee for the study was not required. CT colonographic measurement was performed by two independent radiologists by using two-dimensional (2D) optimized multiplanar reformatted planes and three-dimensional (3D) endoluminal views. Optical colonoscopic measurement was performed by two independent gastroenterologists by using open biopsy forceps. Interobserver agreement, measurement error, measurement discrepancy defined as the result of subtracting the optical colonoscopic measurement from the CT colonographic measurement, and false-mismatch (ie, designation of matched polyps as mismatched between both modalities) rates according to different matching criteria were analyzed.
  
  
  RESULTS
  Intraclass correlation coefficients were 0.879 (95% confidence interval: 0.780, 0.930) for optical colonoscopy, 0.979 (95% confidence interval: 0.956, 0.989) for 2D CT colonography, and 0.985 (95% confidence interval: 0.976, 0.990) for 3D CT colonography. The mean standardized polyp size +/- standard deviation for each observer was 76.3% +/- 14.7 and 85.3% +/- 18.8 for optical colonoscopy, 104.6% +/- 11.6 and 101.6% +/- 10.1 for 2D CT colonography, and 114% +/- 12.4 and 113.4% +/- 13.2 for 3D CT colonography. These values indicated that there was a statistically significant difference among the methods (P<.001). Measurement discrepancy was not proportional to polyp size. A percentage-of-error criterion showed increasing false-mismatch rates with decreasing polyp size, whereas a fixed margin-of-error criterion resulted in more uniform false-mismatch rates across polyp size.
  
  
  CONCLUSIONS
  CT colonography is more reliable and accurate than optical colonoscopy for polyp measurement. A fixed margin-of-error criterion is better than a percentage-of-error criterion for polyp matching between CT colonography and optical colonoscopy with open biopsy forceps.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Eugene K
authors.initials: EK
authors.lastname: Choi
authors.forename: Seung Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Jeong-Sik
authors.initials: JS
authors.lastname: Byeon
authors.forename: Ji-Yun
authors.initials: JY
authors.lastname: Jo
authors.forename: Young Hoon
authors.initials: YH
authors.lastname: Kim
authors.forename: Kyoung Ho
authors.initials: KH
authors.lastname: Lee
authors.forename: Hyun Kwon
authors.initials: HK
authors.lastname: Ha
authors.forename: Joon Koo
authors.initials: JK
authors.lastname: Han
mesh_terms: D000818:Animals; D001706:Biopsy; D003111:Colonic Polyps / Q000000981:diagnostic imaging / Q000473:pathology*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy / Q000379:methods*; D055095:Optics and Photonics; D011446:Prospective Studies; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D013525:Surgical Instruments; D013552:Swine