Pulmonary embolism

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Author: Mikael Häggström [notes 1]


Need for investigation

The indication can effectively be determined by clinical scoring, followed by D-dimer in those less likely to have pulmonary embolism.[1] By Well's score, CT is indicated at a score over 4:[1]

Feature Points
Signs and symptoms of deep vein thrombosis, at least with leg swelling and pain upon palpation of deep veins. 3
No alternative diagnosis better explains the presentation 3
Heart rate over 100/min 1.5
Immobilization >3 days or surgery in past 4 weeks 1.5
Previous pulmonary embolism or deep vein thrombosis 1.5
Hemoptysis 1
Malignancy (current or treated in the past 6 months) 1

Choice of modality

Radiologist algorithm for pulmonary embolism.png

The threshold for normal versus high D-dimer is generally 500 ng/mL or 0.5 mg/L.[2] In pregnant or elderly patients, corresponding D-dimer ranges need to be used.[notes 2]

Further information on modalities:


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.
  2. Pregnant patients
    Upper limit of reference range for D-dimer:
    Units Nonpregnant
    First trimester Second trimester Third trimester
    mg/L or µg/mL < 0.5 < 0.95 < 1.29 < 1.7
    µg/L or ng/mL < 500 < 950 < 1290 < 1700
    nmol/L < 2.7 < 5.2 < 7.1 < 9.3

    Reference: Reference Values During Pregnancy at perinatology.com. Retrieved October 2014.

    Elderly patients

    Patient’s age in years × 10 µg/L (or x 0.056 nmol/L) for patients aged over 50 years for the suspicion of venous thromboembolism (VTE).

    ". J Fam Pract 63 (3): 155–8. March 2014. PMID 24701602. 

    • Raja, Ali S.; Greenberg, Jeffrey O.; Qaseem, Amir; Denberg, Thomas D.; Fitterman, Nick; Schuur, Jeremiah D. (29 September 2015). "Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians

    ". Annals of Internal Medicine 163 (9): 701. doi:10.7326/M14-1772. PMID 26414967. 


  1. 1.0 1.1 Writing Group for the Christopher Study Investigators (2006). "Effectiveness of Managing Suspected Pulmonary Embolism Using an Algorithm Combining Clinical Probability, D-Dimer Testing, and Computed Tomography ". JAMA 295 (2): 172. doi:10.1001/jama.295.2.172. ISSN 0098-7484. 
  2. "Plasma measurement of D-dimer levels for the early diagnosis of ischemic stroke subtypes ". Archives of Internal Medicine 162 (22): 2589–93. 2002. doi:10.1001/archinte.162.22.2589. PMID 12456231. Archived from the original. .