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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
  1. Young Hoon Yoon1,
  2. Sung Woo Lee1,
  3. Dong Min Jung1,
  4. Sung Woo Moon1,
  5. Jan Kurt Horn2,
  6. Yun-Sik Hong2
  1. 1Department of Emergency Medicine, College of Medicine, Korea University, Seoul, Korea
  2. 2Department of Surgery, San Francisco General Hospital, University of California San Francisco, San Francisco, CA, USA
  1. Correspondence to Professor Sung-Woo Lee, Korea University Ansan Hospital Emergency Department, 516 Gojan-dong, Danwon-gu, Ansan 425-707, Korea; kuedlee{at}


Purpose 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.

  • Alveolar dead space fraction
  • clinical probability
  • D-dimer
  • diagnosis
  • end-tidal carbon dioxide
  • pulmonary embolism
  • respiratory
  • thrombo-embolic disease

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  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Korea University Ansan Hospital.

  • Provenance and peer review Not commissioned; externally peer reviewed.