title: Accuracy of very low pretest probability estimates for pulmonary embolism using the method of attribute matching compared with the Wells score.
abstract: OBJECTIVE
  Attribute matching matches an explicit clinical profile of a patient to a reference database to estimate the numeric value for the pretest probability of an acute disease. The authors tested the accuracy of this method for forecasting a very low probability of venous thromboembolism (VTE) in symptomatic emergency department (ED) patients.
  
  
  METHODS
  The authors performed a secondary analysis of five data sets from 15 hospitals in three countries. All patients had data collected at the time of clinical evaluation for suspected pulmonary embolism (PE). The criterion standard to exclude VTE required no evidence of PE or deep venous thrombosis (DVT) within 45 days of enrollment. To estimate pretest probabilities, a computer program selected, from a large reference database of patients previously evaluated for PE, patients who matched 10 predictor variables recorded for each current test patient. The authors compared the outcome frequency of having VTE [VTE(+)] in patients with a pretest probability estimate of <2.5% by attribute matching, compared with a value of 0 from the Wells score.
  
  
  RESULTS
  The five data sets included 10,734 patients, and 747 (7.0%, 95% confidence interval [CI] = 6.5% to 7.5%) were VTE(+) within 45 days. The pretest probability estimate for PE was <2.5% in 2,975 of 10,734 (27.7%) patients, and within this subset, the observed frequency of VTE(+) was 48 of 2,975 (1.6%, 95% CI = 1.2% to 2.1%). The lowest possible Wells score (0) was observed in 3,412 (31.7%) patients, and within this subset, the observed frequency of VTE(+) was 79 of 3,412 (2.3%, 95% CI = 1.8% to 2.9%) patients.
  
  
  CONCLUSIONS
  Attribute matching categorizes over one-quarter of patients tested for PE as having a pretest probability of <2.5%, and the observed rate of VTE within 45 days in this subset was <2.5%.
authors.affiliation: Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC, USA. jkline@carolinas.org
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Kline
authors.forename: D Mark
authors.initials: DM
authors.lastname: Courtney
authors.forename: Martin P
authors.initials: MP
authors.lastname: Than
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hogg
authors.forename: Chadwick D
authors.initials: CD
authors.lastname: Miller
authors.forename: Charles L
authors.initials: CL
authors.lastname: Johnson
authors.forename: Howard A
authors.initials: HA
authors.lastname: Smithline
mesh_terms: D003657:Decision Making; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis; D005544:Forecasting; D006801:Humans; D016015:Logistic Models; D011655:Pulmonary Embolism / Q000453:epidemiology*; D012372:ROC Curve; D054556:Venous Thromboembolism / Q000175:diagnosis / Q000453:epidemiology*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D