Does D-dimer rule out PE? YES, but…

Written by Zach Adams, OSU EM resident // Edited by Michael Barrie EM Assistant Professor.

Bottom line: D-dimer reliably excludes PE in low/moderate risk patients, however use clinical history/exam to guide pursuing advanced imaging.

An otherwise healthy 23 year-old presents with worsening shortness of breath for the past 7 days.  Shortness of breath began suddenly while at rest, has been continuous, and with associated reduced exercise tolerance.  Five days ago she was seen in the ED with a negative d-dimer and CXR and discharged with return precautions.  Since then, she states that the symptoms have progressed. She says she cannot lie flat.  ROS reveals a history of antecedent URI 10 days ago.  She is a non-smoker, takes no birth control pills, does not have a personal or family history of DVT or PE, and denies recent prolonged travel.  She appears uncomfortable and takes deep inspirations every 3-5 seconds.  Her physical exam reveals tachypnea with otherwise normal exam.  ECG shows normal sinus rhythm.  CXR is normal and repeat d-dimer is negative.

The patient has bounced back with worsening symptoms.  I struggled with this clinical question: should we obtain a CT PE to rule out PE despite a negative d-dimer in this low risk patient?

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