• Marc A Rodger, Elana Maser, Ian Stiell, Heather E A Howley, and Philip S Wells.
• Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada. mrodger@ohri.ca
• Thromb. Res. 2005 Jan 1; 116 (2): 101-7.

IntroductionPretest 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).Materials And MethodsA 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).ResultsOne 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).ConclusionsGiven 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.

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