title: Polyp measurement and size categorisation by CT colonography: effect of observer experience in a multi-centre setting.
abstract: The extent measurement error on CT colonography influences polyp categorisation according to established management guidelines is studied using twenty-eight observers of varying experience to classify polyps seen at CT colonography as either 'medium' (maximal diameter 6-9 mm) or 'large' (maximal diameter 10 mm or larger). Comparison was then made with the reference diameter obtained in each patient via colonoscopy. The Bland-Altman method was used to assess agreement between observer measurements and colonoscopy, and differences in measurement and categorisation was assessed using Kruskal-Wallis and Chi-squared test statistics respectively. Observer measurements on average underestimated the diameter of polyps when compared to the reference value, by approximately 2-3 mm, irrespective of observer experience. Ninety-five percent limits of agreement were relatively wide for all observer groups, and had sufficient span to encompass different size categories for polyps. There were 167 polyp observations and 135 (81%) were correctly categorised. Of the 32 observations that were miscategorised, 5 (16%) were overestimations and 27 (84%) were underestimations (i.e. large polyps misclassified as medium). Caution should be exercised for polyps whose colonographic diameter is below but close to the 1-cm boundary threshold in order to avoid potential miscategorisation of advanced adenomas.
authors.affiliation: Intestinal Imaging Centre, St. Marks Hospital, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Burling
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
authors.forename: Wendy
authors.initials: W
authors.lastname: Atkin
authors.forename: Clive
authors.initials: C
authors.lastname: Bartram
authors.forename: Helen
authors.initials: H
authors.lastname: Fenlon
authors.forename: Andrea
authors.initials: A
authors.lastname: Laghi
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
authors.forename: Stuart
authors.initials: S
authors.lastname: Taylor
authors.forename: Roger
authors.initials: R
authors.lastname: Frost
authors.forename: Guido
authors.initials: G
authors.lastname: Dessey
authors.forename: Melinda
authors.initials: M
authors.lastname: De Villiers
authors.forename: Jasper
authors.initials: J
authors.lastname: Florie
authors.forename: Shane
authors.initials: S
authors.lastname: Foley
authors.forename: Lesley
authors.initials: L
authors.lastname: Honeyfield
authors.forename: Riccardo
authors.initials: R
authors.lastname: Iannaccone
authors.forename: Teresa
authors.initials: T
authors.lastname: Gallo
authors.forename: Clive
authors.initials: C
authors.lastname: Kay
authors.forename: Philippe
authors.initials: P
authors.lastname: Lefere
authors.forename: Andrew
authors.initials: A
authors.lastname: Lowe
authors.forename: Filipo
authors.initials: F
authors.lastname: Mangiapane
authors.forename: Jesse
authors.initials: J
authors.lastname: Marrannes
authors.forename: Emmanuele
authors.initials: E
authors.lastname: Neri
authors.forename: Giulia
authors.initials: G
authors.lastname: Nieddu
authors.forename: David
authors.initials: D
authors.lastname: Nicholson
authors.forename: Alan
authors.initials: A
authors.lastname: O'Hare
authors.forename: Sante
authors.initials: S
authors.lastname: Ori
authors.forename: Benedetta
authors.initials: B
authors.lastname: Politi
authors.forename: Martin
authors.initials: M
authors.lastname: Poulus
authors.forename: Daniele
authors.initials: D
authors.lastname: Regge
authors.forename: Lisa
authors.initials: L
authors.lastname: Renaut
authors.forename: Velauthan
authors.initials: V
authors.lastname: Rudralingham
authors.forename: Saverio
authors.initials: S
authors.lastname: Signoretta
authors.forename: Paola
authors.initials: P
authors.lastname: Vagli
authors.forename: Victor
authors.initials: V
authors.lastname: Van der Hulst
authors.forename: Jane
authors.initials: J
authors.lastname: Williams-Butt
mesh_terms: D016009:Chi-Square Distribution; D002983:Clinical Competence; D003111:Colonic Polyps / Q000000981:diagnostic imaging* / Q000473:pathology; D023881:Colonography, Computed Tomographic; D003113:Colonoscopy; D003937:Diagnosis, Differential; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D018709:Statistics, Nonparametric