Pulmonary Embolism: Investigation

Key points

• NICE NG158: history, examination and CXR for all suspected PE, then a two-level PE Wells score. Wells > 4 = PE likely → immediate CTPA. Wells ≤ 4 → D-dimer, CTPA only if positive.
• Wells score: clinical signs of DVT 3 · alternative diagnosis less likely than PE 3 · HR > 100/min 1.5 · immobilisation > 3 days or surgery within 4 weeks 1.5 · previous DVT/PE 1.5 · haemoptysis 1 · malignancy 1.
• If imaging is delayed, give interim anticoagulation — now a DOAC (apixaban or rivaroxaban) rather than LMWH, so that it can simply be continued if PE is confirmed.
• Use a V/Q SPECT (or planar V/Q) instead of CTPA if there is contrast allergy, creatinine clearance < 30 ml/min, or high irradiation risk · a negative CTPA means no further PE investigation or treatment.
• Age-adjusted D-dimer thresholds are used over 50, and PERC can help avoid imaging in low-risk under-50s.
• Test characteristics: D-dimer sensitivity 95-98% with poor specificity · V/Q sensitivity 98%, specificity 40% · S1Q3T3 appears in no more than 20% · CTPA may miss subsegmental emboli.

Decision points in this pathway

• Wells score more than 4 points (PE likely)?
• D-dimer positive?

The full step-by-step algorithm, including what to do at each branch, opens in the app for approved members.