title: Elevated d-dimer cut-off values for computed tomography pulmonary angiography-d-dimer correlates with location of embolism.
abstract: BACKGROUND
  Acute pulmonary embolism (APE) is a potentially fatal condition, and making a timely diagnosis can be challenging. Computed tomography pulmonary angiography (CTPA) has become the modality of choice, and this contributes to the increasing load on emergency room CT scanners. Our purpose was to investigate whether an elevated d-dimer cut-off could reduce the demand for CTPA while maintaining a high sensitivity and negative predictive value (NPV).
  
  
  METHODS
  We retrospectively reviewed all patients referred for CTPA with suspicion of APE in 2012, and collected d-dimer values and CTPA results. We investigated the diagnostic performance of d-dimer using a 0.5 mg/L cut-off and an age adjusted cut-off. We also evaluated a new and elevated cut-off. Cases were categorized according to their CTPA result into: no embolism, peripheral embolism, lobar embolism and central embolism. Finally we investigated a possible correlation between d-dimer values and location of embolism.
  
  
  RESULTS
  We included 1,051 CTPAs, from which 216 (21%) showed pulmonary embolism. There were concomitant d-dimer analyses in 822 CTPA examinations. The current 0.5 mg/L cut-off achieved a sensitivity and NPV of 99%. The age-adjusted cut-off achieved a sensitivity and NPV of 98%, and our suggested cut-off of 0.9 mg/L achieved a sensitivity and NPV of 97%.
  
  
  CONCLUSIONS
  We conclude that the elevated d-dimer cut-off of 0.9 mg/L achieved a high sensitivity and NPV, while reducing the number of CTPA by 27%. The correlation between d-dimer values and location of embolisms supports the suggestion of an elevated d-dimer value.
authors.affiliation: 1 Department of Radiology, Akershus University Hospital, Postboks 1000, 1478 Lørenskog, Norway ; 2 Institute of Clinical Medicine, University of Oslo, Akershus University Hospital, Att: Campus Ahus, Postboks 1000, 1478 Lørenskog, Norway ; 3 Department of Pulmonary Medicine, Gentofte University Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.
authors.forename: Mateuzs Piotr
authors.initials: MP
authors.lastname: Kubak
authors.affiliation: 1 Department of Radiology, Akershus University Hospital, Postboks 1000, 1478 Lørenskog, Norway ; 2 Institute of Clinical Medicine, University of Oslo, Akershus University Hospital, Att: Campus Ahus, Postboks 1000, 1478 Lørenskog, Norway ; 3 Department of Pulmonary Medicine, Gentofte University Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.
authors.forename: Peter Mæhre
authors.initials: PM
authors.lastname: Lauritzen
authors.affiliation: 1 Department of Radiology, Akershus University Hospital, Postboks 1000, 1478 Lørenskog, Norway ; 2 Institute of Clinical Medicine, University of Oslo, Akershus University Hospital, Att: Campus Ahus, Postboks 1000, 1478 Lørenskog, Norway ; 3 Department of Pulmonary Medicine, Gentofte University Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.
authors.forename: Arne
authors.initials: A
authors.lastname: Borthne
authors.affiliation: 1 Department of Radiology, Akershus University Hospital, Postboks 1000, 1478 Lørenskog, Norway ; 2 Institute of Clinical Medicine, University of Oslo, Akershus University Hospital, Att: Campus Ahus, Postboks 1000, 1478 Lørenskog, Norway ; 3 Department of Pulmonary Medicine, Gentofte University Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.
authors.forename: Espen Asak
authors.initials: EA
authors.lastname: Ruud
authors.affiliation: 1 Department of Radiology, Akershus University Hospital, Postboks 1000, 1478 Lørenskog, Norway ; 2 Institute of Clinical Medicine, University of Oslo, Akershus University Hospital, Att: Campus Ahus, Postboks 1000, 1478 Lørenskog, Norway ; 3 Department of Pulmonary Medicine, Gentofte University Hospital, Kildegårdsvej 28, 2900 Hellerup, Denmark.
authors.forename: Haseem
authors.initials: H
authors.lastname: Ashraf
keywords: Computed tomography; pulmonary embolism; sensitivity