title: The additional use of end-tidal alveolar dead space fraction following D-dimer test to improve diagnostic accuracy for pulmonary embolism in the emergency department.
abstract: OBJECTIVE
  To determine the diagnostic performance of bedside assessment of end-tidal alveolar dead space fraction (ADSF) for pulmonary embolism (PE) and whether the use of additional ADSF assessment following D-dimer assay can improve the diagnostic accuracy in suspected PE patients in the emergency department.
  
  
  METHODS
  A prospective observational study of 112 consecutive adult patients suspected of PE of whom 102 were eligible for analysis. ADSF was calculated using arterial carbon dioxide and end-tidal carbon dioxide. An ADSF less than 0.2 was considered normal.
  
  
  RESULTS
  PE was confirmed in 11 (10.8%) of 102 patients. D-dimer assay alone as a reference standard test for PE had a sensitivity of 100%, specificity of 38.5% and false negativity of 0%. Area under the receiver-operator characteristic curve for the diagnosis of PE using ADSF values alone was 0.894, Sensitivity, specificity and false negativity for the combined results of a positive D-dimer test and abnormal ADSF were 100%, 78.0% and 0% for the presence of PE, respectively. Of 65 patients with a low or intermediate clinical probability and a positive D-dimer assay, 36 (55.4%) patients displayed normal ADSF and had no PE.
  
  
  CONCLUSIONS
  By itself ADSF assessment performed well in diagnosis of PE. The combined result of a positive D-dimer and abnormal ADSF increased the specificity for diagnosing PE compared with the D-dimer test alone. The use of additional bedside ADSF assessment following a positive D-dimer test may reduce the need for further imaging studies to detect PE in patients with a low or intermediate clinical probability.
authors.affiliation: Department of Emergency Medicine, College of Medicine, Korea University, Seoul, Korea.
authors.forename: Young Hoon
authors.initials: YH
authors.lastname: Yoon
authors.forename: Sung Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Dong Min
authors.initials: DM
authors.lastname: Jung
authors.forename: Sung Woo
authors.initials: SW
authors.lastname: Moon
authors.forename: Jan Kurt
authors.initials: JK
authors.lastname: Horn
authors.forename: Yun-Sik
authors.initials: YS
authors.lastname: Hong
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D019296:Capnography; D002245:Carbon Dioxide / Q000032:analysis; D004636:Emergency Service, Hospital; D005188:False Negative Reactions; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D017052:Hospital Mortality; D006785:Hospitals, University; D006801:Humans; D007723:Korea; D008297:Male; D008875:Middle Aged; D019370:Observation; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000503:physiopathology; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000401:mortality; D015203:Reproducibility of Results; D012126:Respiratory Dead Space / Q000502:physiology; D012129:Respiratory Function Tests; D056152:Respiratory Rate / Q000502:physiology; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D002245:Carbon Dioxide