Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Move from a non-specific presentation to a defensible pulmonary embolism diagnosis using clinical probability, D-dimer and the right imaging test without delaying treatment in an unstable patient.
PE symptoms and routine tests are non-specific. The safe diagnostic method is sequential: stability, clinical probability, D-dimer only in the appropriate probability group, then definitive imaging.
D-dimer is a rule-out test in low-probability disease, not a confirmatory test. Infection, cancer, pregnancy, inflammation, age and recent surgery commonly elevate it.
Risk scores support rather than replace judgement. PERC applies only after the clinician has judged the pre-test probability low; the Wells score applies once PE is genuinely suspected.
Pregnancy and the puerperium require a pregnancy-specific diagnostic pathway and multidisciplinary imaging choice; the standard NICE NG158 pathway should not simply be copied across.
Cardiac arrest, obstructive shock, persistent systolic hypotension, rising lactate, altered consciousness or rapidly escalating oxygen need suggests high-risk PE or another immediately reversible cause.
Sudden dyspnoea, pleuritic pain, tachypnoea and tachycardia are common; haemoptysis and syncope are less frequent but increase concern in the right context.
Unilateral leg swelling, deep venous tenderness or a recently confirmed proximal DVT materially increases probability and may provide an alternative diagnostic route when chest imaging is unsafe.
Recent surgery or immobilisation, active cancer, oestrogen exposure, pregnancy/puerperium, previous VTE and thrombophilia change pre-test probability but do not diagnose PE.
ACS, aortic syndrome, pneumothorax, pneumonia, asthma/COPD, acute heart failure, pericarditis, sepsis and panic symptoms can look similar; assess them in parallel when clinically plausible.
Check bleeding, platelet count, renal function, recent neuraxial procedure and heparin-induced thrombocytopenia history. Exact LMWH selection and renal adjustment must follow the current product information.
Do not give routinely to a patient already within target. Severe hypoxaemia or shock warrants immediate senior airway/critical-care assessment.
PERC is not a substitute for Wells in a patient already judged to have meaningful PE probability; using it after deciding PE is likely creates false reassurance.
It only removes the rule-out shortcut. Probability and imaging still determine the diagnosis.
A saddle embolus may be stable, while a smaller clot burden can produce shock in limited cardiopulmonary reserve. Treat physiology and RV failure, not the headline scan phrase.
NICE specifically separates taking baseline bloods from waiting for their results when interim anticoagulation is indicated.
It is particularly useful when iodinated contrast is problematic, but abnormal lungs increase non-diagnostic studies; discuss the modality rather than ordering it reflexively.
Ordering D-dimer in a PE-likely patient and delaying definitive imaging.
Using PERC after deciding the patient has moderate or high clinical probability.
Treating tachycardia, S1Q3T3 or hypoxaemia as a diagnostic test for PE.
Waiting for baseline blood results before giving indicated interim anticoagulation.
Sending a shocked patient to CT without an airway, haemodynamic and reperfusion plan.
Stopping after a negative CTPA without considering DVT or a clinically important alternative diagnosis.
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A haemodynamically stable adult with suspected PE has a 2-level PE Wells score of 6.0. CTPA can be performed within 90 minutes. What is the best next step?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes