title: The TL,NO/TL,COratio cannot be used to exclude pulmonary embolism.
abstract: BACKGROUND
  The existing screening modalities for pulmonary embolism (PE), such as D-dimer and clinical prediction rules, have low positive predictive values. With its capability to indicate pulmonary vascular abnormalities, the ratio of the transfer factor of the lungs for nitric oxide and the transfer factor of the lungs for carbon monoxide (TL,NO/TL,CO) might be an additional discriminating parameter.
  
  
  METHODS
  Carbon monoxide/Nitric oxide diffusion measurements were performed on unselected patients seen on the emergency department for which due to suspected PE a computed tomography pulmonary angiogram (CTPA) was ordered.
  
  
  RESULTS
  A total of 28 patients were included, PE was found in 12 on CTPA. Median TL,NO/TL,COratio was 4·09 (interquartile range (IQR) 3·83-4·40) in the no PE group versus 4·00 (IQR 3·78-4·32) in the PE group (P = 0·959). Median alveolar volume was 77·1% of predicted in the no PE group versus 71·0% of predicted in the PE group (P = 0·353). Median TL,COwas 75·8% of predicted in the no PE group versus 68·8% of predicted in the PE group (P = 0·120). Median TL,NOwas 69·3% of predicted in the no PE group versus 60·5% of predicted in the PE group (P = 0·078).
  
  
  CONCLUSIONS
  The presented data indicate that the TL,NO/TL,COratio cannot be used to exclude PE.
authors.affiliation: Department of Pulmonology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Timon M
authors.identifier: http://orcid.org/0000-0001-7519-0206
authors.initials: TM
authors.lastname: Fabius
authors.affiliation: Department of Pulmonology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Michiel M
authors.initials: MM
authors.lastname: Eijsvogel
authors.affiliation: Department of Pulmonology, Spaarne Hospital, Hoofddorp, The Netherlands.
authors.forename: Ivo
authors.initials: I
authors.lastname: van der Lee
authors.affiliation: Medical School Twente, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Marjolein
authors.initials: M
authors.lastname: Brusse-Keizer
authors.affiliation: Department of Pulmonology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Frans H
authors.initials: FH
authors.lastname: de Jongh
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002248:Carbon Monoxide / Q000097:blood*; D000072226:Computed Tomography Angiography; D004058:Diffusion; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood*; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide; D002248:Carbon Monoxide
keywords: carbon monoxide; diffusing capacity; nitric oxide; pulmonary embolism; transfer factor