title: Prospective multicenter assessment of interobserver agreement for radiologist interpretation of multidetector computerized tomographic angiography for pulmonary embolism.
abstract: BACKGROUND
  Emergency physicians rely on the interpretation of radiologists to diagnose and exclude pulmonary embolism (PE) on the basis of computerized tomographic pulmonary angiography (CTPA). Few data exist regarding the interobserver reliability of this endpoint.
  
  
  OBJECTIVE
  To quantify the degree of agreement in CTPA interpretation between four academic hospitals and an independent reference reading (IRR) laboratory.
  
  
  METHODS
  Hospitalized and emergency department patients who had one predefined symptom and sign of PE and underwent 64-slice CTPA were enrolled from four academic hospitals. CTPA results as interpreted by board-certified radiologists from the hospitals were compared against those from the IRR laboratory. CTPAs were read as indeterminate, PE(-) or PE(+), and percentage obstruction was computed by the IRR laboratory, using a published method. Agreement was calculated with weighted Cohen's kappa.
  
  
  RESULTS
  We enrolled 492 subjects (63% female, age 54 +/- 1 years, and 16.7% PE(+) at the site hospitals). Overall agreement was 429/492 (87.2%; 95% confidence interval 83.9-90.0). We observed 13 cases (2.6%) of complete discordance, where one reading was PE(+) and the other reading was PE(-). Weighted agreement was 92.3%, with kappa = 0.75. The median percentage obstruction for all patients was 9% (25th-75th percentile interquartile range: 5% to -30%). For CTPAs interpreted at the site hospitals as PE(-) or indeterminate but read as PE(+) by the IRR laboratory, the median of percentage obstruction was 6% (4-7%).
  
  
  CONCLUSIONS
  We found in this sample a good level of agreement, with a weighted kappa of 0.75, but with 2.6% of patients having total discordance. Overall, a large proportion of clots were distal or minimally occlusive clots.
authors.affiliation: Department of Emergency Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Courtney
authors.forename: C
authors.initials: C
authors.lastname: Miller
authors.forename: H
authors.initials: H
authors.lastname: Smithline
authors.forename: N
authors.initials: N
authors.lastname: Klekowski
authors.forename: M
authors.initials: M
authors.lastname: Hogg
authors.forename: J A
authors.initials: JA
authors.lastname: Kline
mesh_terms: D000046:Academic Medical Centers / Q000706:statistics & numerical data; D019411:Clinical Laboratory Techniques / Q000706:statistics & numerical data; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007297:Inpatients / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000706:statistics & numerical data*; D014481:United States