title: The interobserver reliability of pretest probability assessment in patients with suspected pulmonary embolism.
abstract: BACKGROUND
  Pretest probability assessment and objective testing are combined to appropriately manage patients with suspected pulmonary embolism (PE). However, the interobserver reliability of pretest probability assessment has not been investigated. We sought to determine (for patients with suspected PE) the interobserver reliability of pretest probability assessment (by overall impression (gestalt) versus an explicit clinical model).
  
  
  METHODS
  A prospective cohort study was conducted at an urban university hospital. For patients referred for ventilation and perfusion (V/Q) scanning for suspected PE, structured assessments (11 history and 4 physical examination parameters) were performed by a referring physician and a designated thrombosis physician. The referring and thrombosis physicians also assigned a pretest probability for PE (low, moderate, or high) by gestalt. An explicit seven-point clinical model for suspected PE was later applied to each structured assessment to determine the pretest probability. Assessments were performed independently and prior to diagnostic test results. Interobserver reliability (two rater unweighted Kappa (kappa) statistic) was determined for each parameter on the structured assessment and the pretest probability assessments (gestalt vs. explicit clinical model).
  
  
  RESULTS
  One hundred and ten patients with suspected PE received duplicate assessments. Historical features demonstrated substantial to almost perfect interobserver reliability (kappa=0.60-0.95). For the physical findings, only heart rate had substantial interobserver reliability (kappa=0.60). Pretest probability assessment was not reliable when using physician's gestalt (kappa=0.33), but produced substantial interobserver reliability using the explicit clinical model (kappa=0.62).
  
  
  CONCLUSIONS
  Given the inadequate interobserver reliability of pretest probability assessment by overall impression (or gestalt), physicians should use explicit clinical models in the diagnostic management of patients with suspected pulmonary embolism.
authors.affiliation: Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada. mrodger@ohri.ca
authors.forename: Marc A
authors.initials: MA
authors.lastname: Rodger
authors.forename: Elana
authors.initials: E
authors.lastname: Maser
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.forename: Heather E A
authors.initials: HE
authors.lastname: Howley
authors.forename: Philip S
authors.initials: PS
authors.lastname: Wells
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011336:Probability; D011655:Pulmonary Embolism / Q000175:diagnosis*