Diagnosis of pulmonary embolism

The diagnosis of pulmonary embolism is difficult. Positive results from ventilation-perfusion scanning or pulmonary arteriography confirm the diagnosis whilst a normal D-dimer makes the diagnosis of a pulmonary embolism very unlikely.

If a diagnosis of pulmonary embolism is suspected on the basis of history and clinical examination then urgent, and immediate, referral for secondary care review is indicated.

If pulmonary embolism (PE) is suspected and with a likely two-level PE Wells score then undertake either:

• an immediate computed tomography pulmonary angiogram (CTPA) or
  
  
• immediate interim parenteral anticoagulant therapy followed by a CTPA, if a CTPA cannot be carried out immediately.

If the CTPA is negative and DVT is suspected then consider a proximal leg vein ultrasound scan

If PE is suspected and with an unlikely two-level PE Wells score, then off a D-dimer test and if the result is positive offer either:

• an immediate CTPA or
• immediate interim parenteral anticoagulant therapy followed by a CTPA, if a CTPA cannot be carried out immediately

Notes:

• if patient has an allergy to contrast media, or who have renal impairment, or whose risk from irradiation is high:
  • assess the suitability of a ventilation/perfusion single photon emission computed tomography (V/Q SPECT) scan or, if a V/Q SPECT scan is not available, a V/Q planar scan, as an alternative to CTPA
  • if offering a V/Q SPECT or planar scan that will not be available immediately, offer immediate interim parenteral anticoagulant therapy

Reference:

1. NICE. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. NG158. Published: 26 March 2020. Last updated: 02 August 2023