Interobserver Variation of Colonic Polyp Measurement at Computed Tomography Colonography |
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Authors: | Gurjeet Dulku Chandra Hewavitharana Tonya Halliday Duncan Ramsay Richard Ho Michael Phillips Richard Mendelson |
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Affiliation: | 1. Department of Diagnostic and Interventional Radiology, Royal Perth Hospital, Perth, Western Australia;2. Harry Perkins Institute for Medical Research, University of Western Australia, Perth, Western Australia;3. Centre for Medical Research, University of Western Australia, Perth, Western Australia |
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Abstract: | BackgroundThe concept of “advanced polyps” is well accepted and is defined as polyps ≥10 mm and/or those having a villous component and/or demonstrating areas of dysplasia. Of these parameters, computed tomography colonography (CTC) can only document size. The accepted management of CTC-detected “advanced polyps” is to recommend excision if feasible, whereas the management of “intermediate” (6–9 mm) polyps is more controversial, and interval surveillance may be acceptable. Therefore, distinction between 6-9 mm and ≥10 mm is important.MethodsDatasets containing 26 polyps originally reported as between 8-12 mm in diameter were reviewed independently by 4 CTC-accredited radiologists. Observers tabulated the largest measurement for each polyp on axial, coronal, sagittal, and endoluminal views at lung-window settings. These measurements were also compared to those determined by the computer-aided detection (CAD) software.ResultsThe interobserver reliability intra-class correlation coefficient (ICC) for sagittal projection was 0.80 (“excellent” category of Hosmer and Lemeshow [2004]), 0.71 for axial (“acceptable”), 0.69 for coronal, and 0.41 for endoluminal (“unacceptable”). The largest of sagittal/axial/coronal measurement gave the best reliability with the smallest variance (ICC = 0.80; 95% CI 0.67–0.89). For 8 of 26 polyps, at least one radiologist's measurement placed the polyp in a different category compared to a colleague. For the majority of the polyps, the CAD significantly overestimated the readings compared to the largest of the manual measurements with an average difference of 1.6 mm (P < .0001 for sagittal/axial/coronal). This resulted in 33% of polyps falling into a different category—10% were lower and 23% were higher (P < .034).ConclusionIt is apparent that around the cutoff point of 10 mm between “advanced” and “intermediate” polyps, interobserver performance is variable. |
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Keywords: | Address for correspondence: Gurjeet Dulku, MBBS, Department of Diagnostic and Interventional Radiology, (Level 3, North Block), Royal Perth Hospital, 197, Wellington Street, 6000 Perth, Western Australia. Colonic polyp Computed tomographic colonography Virtual colonoscopy Computer-aided detection Observer variation |
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