Go directly to the Diagnostic algorithm 

See Clinical scoring systems for PE - Wells or Geneva criteria

See Management of PE

PE = pulmonary embolus
CTPA = Computer Tomography Pulmonary Angiogram
V/Q scan = Ventilation / Perfusion scan
PA = Pulmonary Angiogram
NPV = Negative predictive value


  • PE is often an elusive diagnosis (only about 10% of patients have a clear clinical presentation)
  • Non-diagnostic V/Q scans (low, intermediate, indeterminate) are not sufficiently useful to confirm or exclude PE
  • Although PE can be fatal, the risk of untreated PE is not entirely known
  • The annual risk of major bleeding from anti-coagulation varies from 0-4% depending on co-morbidities (the riskiest period is in the first month of treatment)
  • The critical step in assessment is to estimate the clinical likelihood of PE (see Clinical scoring systems for PE)
  • In high risk or moderately symptomatic patients, anti-coagulate prior to imaging (if no contraindications)
  • If severely symptomatic consider thrombolysis

Diagnostic features

Any of the following in which an alternative diagnosis cannot be found

See the Diagnostic algorithm (this algorithm has > 99% accuracy)

Clinical probability testing

  • This is the critical step prior to further testing
  • The pre-test probability markedly influences the interpretation of subsequent d-dimer, V/Q or CTPA results
  • It is prudent to obtain a haematology opinion prior to discharging a high risk patient in which the diagnosis of PE has not been made

 (see Clinical scoring systems for PE)


  • Only has sufficient NPV in non-high clinical probability of PE (a negative d-dimer result CANNOT rule out PE in high clinical probability and should not be performed)
  • D-dimer > 0.5mg/L mandates further imaging

V/Q scan

(see Predictive value according to clinical probability)


  • Recent studies indicate a negative CT in a non-high probability patient effectively rules out PE
  • With shielding, there is a lower fetal radiation dose than V/Q

Combination testing

  • In patients with high pre-test probability for thrombo-embolic disease neither a normal leg U/S, V/Q scan or CTPA can exclude PE (PA is required)

Risk of Angiography

  • Death 
  • Serious cardiorespiratory complications
  • Minor anaphylactic reactions/renal deterioration 


) seen mainly in critically ill patients

Risk of Anticoagulation

  • The risk of major bleeding from anti-coagulation varies from 1-4% per year depending on a patients risk profile.

(see Estimating risk of bleeding from anticoagulation)