What is the recommended work‑up for a suspected pulmonary embolism?

Pulmonary Embolism Work-Up

Begin by assessing clinical probability using a validated scoring system, then proceed with D-dimer testing in low/intermediate probability patients or proceed directly to CT pulmonary angiography (CTPA) in high probability patients, while initiating anticoagulation immediately in intermediate or high probability cases before imaging confirmation. 1

Initial Clinical Assessment

Most patients with PE present with breathlessness and/or tachypnea >20 breaths/min; in the absence of these findings, pleuritic chest pain or hemoptysis is usually due to another cause. 1

Clinical Probability Stratification

Assess clinical probability by asking two key questions: 1

• Is another diagnosis unlikely? (chest radiograph and ECG are helpful for excluding alternatives)
• Is a major risk factor present? (recent immobilization/major surgery, lower limb trauma or surgery, pregnancy/postpartum, major medical illness, previous proven VTE)

Scoring: 1

• Low probability = neither criterion present
• Intermediate probability = either criterion present
• High probability = both criteria present

Alternatively, use the Wells score or revised Geneva score to stratify patients into probability categories. 2

Baseline Testing

Obtain these tests in all patients with suspected PE: 1, 2

• Chest radiograph (abnormal in >80% of PE cases, though findings are non-specific; helps exclude alternative diagnoses) 2
• ECG (may reveal right ventricular strain patterns: T-wave inversion V1-V4, S1Q3T3, right bundle branch block) 2
• Arterial blood gas (does not have sufficient sensitivity/specificity to confirm or exclude PE, but helps assess clinical probability) 3

Critical pitfall: Up to 40% of patients with PE have normal arterial oxygen saturation—normal SaO₂ should never be used to exclude PE. 2

Diagnostic Algorithm for Non-Massive PE

Step 1: D-Dimer Testing (Selective Use)

D-dimer should only be performed after clinical probability assessment and has strict limitations: 1

Do NOT perform D-dimer if: 1

• Alternative diagnosis is highly likely
• Clinical probability is HIGH
• Probable massive PE is present
• Patient is hospitalized with infection, cancer, inflammation, or recent surgery (D-dimer will be elevated in <10% of these cases) 1

Validated D-dimer assays that reliably exclude PE when negative: 1

• SimpliRED (agglutination): for LOW clinical probability only
• Vidas (ELISA): for LOW or INTERMEDIATE clinical probability (cutoff <500 μg/L)
• MDA (latex): for LOW or INTERMEDIATE clinical probability

If D-dimer is negative in appropriate patients, PE is excluded and no further testing is needed. 1, 3

Step 2: Lower Extremity Venous Ultrasound

Leg ultrasound is an alternative to lung imaging in patients with clinical signs of DVT. 1

• If DVT is confirmed, treat for VTE without requiring lung imaging 1
• If ultrasound is normal but D-dimer is elevated, proceed with lung imaging (50% of PE patients have normal leg ultrasound) 1

Step 3: Imaging

CTPA is now the recommended initial lung imaging modality for non-massive PE. 1

• Patients with good quality negative CTPA do not require further investigation or treatment for PE 1
• CTPA allows visualization of pulmonary thromboemboli down to the segmental level and assessment of RV enlargement 4

Isotope lung scanning (V/Q scan) may be considered as initial imaging IF: 1

• Facilities are available on-site, AND
• Chest radiograph is normal, AND
• No significant symptomatic concurrent cardiopulmonary disease, AND
• Standardized reporting criteria are used, AND
• Non-diagnostic results are always followed by further imaging

V/Q scan interpretation: 1

• Normal scan = PE excluded
• Low probability scan + low clinical probability = PE excluded
• High probability scan + high clinical probability = PE present
• Any other combination = requires CTPA or pulmonary angiography

Important caveat: Indeterminate V/Q scans require additional imaging rather than management based solely on clinical features. 2

Step 4: Management of Discordant Results

In patients with high clinical probability and negative CTPA, valid options are: 1

• Conclude PE has been excluded and stop heparin
• Consider further imaging for VTE (leg ultrasound, conventional pulmonary angiography)
• Seek specialist advice

Diagnostic Algorithm for Massive PE

Massive PE is highly likely if: 1

• Collapse/hypotension, AND
• Unexplained hypoxia, AND
• Engorged neck veins, AND
• Right ventricular gallop (often)

The most useful initial test is echocardiography, which shows indirect signs of acute pulmonary hypertension and right ventricular overload. 1

CTPA or echocardiography will reliably diagnose clinically massive PE. 1

• In highly unstable patients, thrombolytic treatment may be initiated based on compatible echocardiographic findings alone 1
• If the patient is stabilized, seek definitive diagnosis with CTPA 1
• A normal lung scan or CTPA should prompt search for another cause of shock 1

Immediate Anticoagulation

Initiate heparin therapy immediately in patients with intermediate or high clinical probability before imaging confirmation. 1, 2

• Unfractionated heparin (UFH) should be considered: 1

  • As first dose bolus (80 units/kg IV) 1
  • In massive PE
  • Where rapid reversal of effect may be needed

• Low molecular weight heparin (LMWH) is preferable to UFH in non-massive PE, having equal efficacy and safety and being easier to use 1

Common Pitfalls to Avoid

• Never use D-dimer as a routine screening test—it should only be ordered after clinical probability assessment 1
• Do not rely on normal oxygen saturation to rule out PE (occurs in ~40% of cases) 2
• Do not perform D-dimer in high probability patients or hospitalized patients with comorbidities (low yield) 1
• Do not order V/Q scan if chest X-ray is abnormal or patient has chronic cardiopulmonary disease (will likely be non-diagnostic) 1
• Imaging should be performed within 1 hour in massive PE and ideally within 24 hours in non-massive PE 1, 2