title: Evaluation of individual criteria for low probability interpretation of ventilation-perfusion lung scans.
abstract: The purpose of this investigation was to identify characteristics or combinations of characteristics of the ventilation-perfusion (V/Q) scan in patients with suspected acute pulmonary embolism (PE) can be used for a "very low probability" interpretation ( < 10% positive predictive value).
  
  
  METHODS
  Data were culled from individual lungs of 532 patients in the randomized arm of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study and 205 patients in the referred arm. All patients had a < 20% consensus probability estimate of PE based on V/Q scan results, and all underwent pulmonary angiography.
  
  
  RESULTS
  Nonsegmental perfusion abnormalities, perfusion defects smaller than opacities on the chest radiograph, a combination of these types of perfusion abnormalities, and matched V/Q abnormalities in two or three zones of a single lung had a positive predictive value < 10%. These criteria can therefore be used for a very low probability interpretation. A matched V/Q defect in only one zone of the lung had a positive predictive value greater than 10% and is not a criterion for low probability. Perfusion defects associated with small pleural effusions (obliteration of the costophrenic angle) had a positive predictive value of 25%-33%, depending on the group studied, and are a criterion for intermediate probability.
  
  
  CONCLUSIONS
  Criteria appropriate for a very low probability ( < 10% positive predictive value) interpretation of V/Q scans in patients with suspected acute PE have been identified.
authors.affiliation: Henry Ford Heart and Vascular Institute, Detroit, Michigan 48202-2691, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Stein
authors.forename: B
authors.initials: B
authors.lastname: Relyea
authors.forename: A
authors.initials: A
authors.lastname: Gottschalk
mesh_terms: D005069:Evaluation Studies as Topic; D006331:Heart Diseases / Q000453:epidemiology; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging* / Q000453:epidemiology; D011859:Radiography; D011877:Radionuclide Imaging; D011897:Random Allocation; D014692:Ventilation-Perfusion Ratio