title: Utility of lower extremity venous ultrasound scanning in the diagnosis and exclusion of pulmonary embolism in outpatients.
abstract: OBJECTIVE
  Emergency physicians frequently rely on normal findings from a lower extremity venous ultrasound examination as a method to decrease the probability of pulmonary embolism (PE) in outpatients with a nondiagnostic ventilation-perfusion lung scan (V/Q scan). The objective of this study was to evaluate the diagnostic utility of bilateral lower extremity venous ultrasound scanning in the diagnosis of PE in emergency department patients with a low-, moderate-, or indeterminate-probability (nondiagnostic) V/Q scan.
  
  
  METHODS
  This prospective, 2-center, descriptive study was conducted at the EDs of 2 large teaching hospitals. From an initial cohort of 570 nonreferred outpatients, a convenience sample of 156 patients who had both a nondiagnostic V/Q scan and a lower extremity venous ultrasound scan performed was selected as the study population. The sensitivity and specificity for a single lower extremity venous ultrasound scan and the posttest probability of PE were determined for the study population.
  
  
  RESULTS
  In the study population, the best-case sensitivity of the lower extremity venous ultrasound scan for PE was 54% (95% confidence interval [CI] 37% to 71%) and the specificity was 98% (95% CI 94% to 100%). The likelihood ratio of a positive test result was 27. The likelihood ratio of a negative test result was 0.49, yielding a lowest possible posttest probability of PE of 12% (95% CI 6% to 17%).
  
  
  CONCLUSIONS
  This study demonstrates that the combination of a nondiagnostic (low, moderate, or indeterminate) V/Q scan plus a single negative result from lower extremity venous ultrasound examination, even in a best-case scenario, does not exclude the diagnosis of PE.
authors.affiliation: Oklahoma State University-College of Osteopathic Medicine, Tulsa, OK, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Daniel
authors.forename: R E
authors.initials: RE
authors.lastname: Jackson
authors.forename: J A
authors.initials: JA
authors.lastname: Kline
mesh_terms: D000328:Adult; D000368:Aged; D000553:Ambulatory Care; D003937:Diagnosis, Differential; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D013924:Thrombophlebitis / Q000000981:diagnostic imaging*; D014463:Ultrasonography; D014680:Veins / Q000000981:diagnostic imaging; D014692:Ventilation-Perfusion Ratio / Q000502:physiology