title: Comparison between tracheal ratio methods used by three observers at three occasions in English Bulldogs.
abstract: BACKGROUND
  Tracheal hypoplasia is a congenital condition described in mainly brachycephalic breeds and is one component of the brachycephalic obstructive airway syndrome (BOAS). Two radiographic methods have been described to evaluate the dimensions of the tracheal diameter in dogs and to distinguish between hypoplastic and non-hypoplastic tracheas: the tracheal lumen diameter to thoracic inlet distance ratio (TD/TI) and the ratio between the thoracic tracheal luminal diameter and the width of the proximal third of the third rib (TT/3R). The purpose of this study was to compare these two published radiographic methods between observers, different measuring occasions and to investigate the effect on classification of dogs as having hypoplastic or non-hypoplastic tracheas using four previously published mean ratios as cut-offs (<0.11, <0.127 and <0.144 for the TD/TI and <2.0 for the TT/3R method). Three observers evaluated right and left lateral recumbent radiographs from 56 adult English Bulldogs independently on three different occasions. TD/TI and TT/3R ratios were calculated and correlated between measuring occasions. Kappa, observed, positive, and negative agreements were calculated between observers and measuring occasions. Number of hypoplastic and non-hypoplastic dogs for each method and occasion was determined using <0.11, <0.127 and <0.144 as cut-offs for TD/TI and <2.0 for TT/3R.
  
  
  RESULTS
  Intraobserver agreement varied with kappa between 0.45-0.94 for the TD/TI and 0.20-0.86 for the TT/3R method. Interobserver kappa varied between 0.27-0.70 for the TD/TI method and between 0.05-0.57 for the TT/3R method. There was poor agreement in classifying English Bulldogs as tracheal hypoplastic or non-hypoplastic, depending on measuring method, cut-off value and observer.
  
  
  CONCLUSIONS
  The diagnostic value of both the TD/TI and TT/3R methods with such poor agreement is questionable, and significantly impacts their reliability for both clinical evaluation of dogs and use in health screening programs.
authors.affiliation: University Animal Hospital, Swedish University of Agricultural Sciences, P.O. Box 7040, SE-750 07, Uppsala, Sweden. jessica.ingman@slu.se.
authors.forename: Jessica
authors.initials: J
authors.lastname: Ingman
authors.affiliation: Alingsås Animal Hospital, Ridhusvägen 4, SE-441 93, Alingsås, Sweden. veronica.naeslund@gmail.com.
authors.forename: Veronica
authors.initials: V
authors.lastname: Näslund
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, P.O. Box 7054, SE-750 07, Uppsala, Sweden. kerstin.hansson@slu.se.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hansson
mesh_terms: D000402:Airway Obstruction / Q000000981:diagnostic imaging / Q000662:veterinary*; D000818:Animals; D003955:Diagnostic Tests, Routine / Q000662:veterinary*; D004283:Dog Diseases / Q000000981:diagnostic imaging*; D004285:Dogs; D005260:Female; D008297:Male; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D013045:Species Specificity