EBQ:Wells PE Rule Out

Under Review Journal Club Article

Wells PS et al. "Excluding Pulmonary Embolism at the Bedside without Diagnostic Imaging: Management of Patients with Suspected Pulmonary Embolism Presenting to the Emergency Department by Using a Simple Clinical Model and D-Dimer". Annals of Internal Medicine. 2001. 135(2):98-107.
PubMed Full text PDF

Clinical Question

Is there a simple clinical model along with d-dimer assay testing that can be used to manage patients presenting to the emergency department with suspected pulmonary embolism?

Conclusion

Patients can be safely managed for suspected pulmonary embolism on the basis of pretest probability and d-dimer

Major Points

Wells Score

Wells Criteria

Clinical Features	Points
Symptoms of DVT (leg swelling and pain with palpation)	3.0
PE as likely as or more likely than an alternative diagnosis	3.0
HR >100 bpm	1.5
Immobilization for >3 consecutive days or surgery in the previous 4 weeks	1.5
Previous DVT or PE	1.5
Hemoptysis	1.0
Malignancy (receiving treatment, treatment stopped within 6 mon, palliative care)	1.0

Two Tier Wells Score

• Score 0-4 = PE Unlikely (12.1% incidence of PE)
  • Check D-dimer
    • If D-dimer positive then obtain CTPA or V/Q scan
    • If D-dimer negative, no further workup needed (0.5% incidence of PE at 3 month follow up)
• Score >4 = PE Likely (37.1% incidence of PE)
  • Obtain CT Pulmonary Angiography or V/Q Scan
• New evidence suggests lower Wells Score with D-dimer <1000 ng/mL is effective at ruling out PE without imaging

PE exclusion:

• Low pre-test probability and negative d-dimer
• Definitive negative imaging needed for moderate and high pretest probability

NPV=99.5% of diagnostic algorithm

Study Design

• Prospective cohort study in 4 Canadian tertiary care hospitals
• Patients were evaluated by 1 of 43 designated EM physicians
• Physician assigned points according to the Well's criteria points table above
• Primary outcome was development of venous thromboembolic event in patients with excluded PE diagnosis during 3 months of follow-up
  • Diagnosis of PE made with high-probability V-P scan, abnormal result on ultrasound or pulmonary angiography, or VTE during follow-up

Population

Patient Demographics

• Mean age: 50.5 years old
• Women: 63%
• Mean duration of symptoms: 3.2 days
• Diagnosis of cancer: 7.2%
• Recent surgery: 8.4%
• Recent immobilization: 7.6%

Inclusion Criteria

• Presenting to participating ED
• Suspicion of PE
• Symptoms for <30 days
• Acute onset of new or worsening shortness of breath or chest pain

Exclusion Criteria

• Suspected DVT of the upper extremity as a likely source of PE
• No symptoms of PE within 3 days of presentation
• Anticoagulant therapy for more than 24 hours
• Expected survival time <3 months
• Contraindication to contrast media
• Pregnancy
• Geographic inaccessibility precluding follow-up
• <18 years old

Interventions

Physicians used a clinical model to determine patients’ pretest probability of pulmonary embolism, then performed a D-dimer test

• Low pretest probability and a negative D-dimer: No further tests, PE excluded
• All other patients underwent ventilation–perfusion lung scanning
  • If nondiagnostic V-P scan, perform bilateral deep venous ultrasonography
  • Further testing (serial ultrasonography or angiography) was done based on patients' pretest probability and lung scanning results

Outcomes

n=930 patients with suspected pulmonary embolism

Primary Outcome

Pretest Probability	Patients	Diagnosis of PE
Low	527	7 (1.3%)
Moderate	339	55 (16.2%)
High	64	24 (40.6%)

• 849 patients had the diagnosis of PE excluded
  • Of these, 5 patients (0.6%) developed PE or DVT during follow-up. However, 4 of these had not undergone the proper diagnostic protocol.
• 437 patients had the diagnosis excluded with a negative D-dimer result and low clinical probability
  • Of these, only 1 developed PE during follow-up

Negative predictive value for combined strategy with D-dimer testing: 99.5% (CI, 99.1% to 100%)

Criticisms & Further Discussion

• This study used V-P lung scan, which was been replaced by CTA as imaging of choice
  • CTA has increased sensitivity (83%) and specificity (96%), compared to 65% and 94%, respectively, for V-P scan
• Clinical gestalt is heavily weighted in this decision rule
  • Having PE as most likely diagnosis automatically classifies the patient as moderate pretest probability
• Wells criteria often used in concert with the PERC rule to increase sensitivity

Funding

Grant from the Heart and Stroke Foundation of Nova Scotia and Ontario

See Also

• EBQ:ADJUST-PE Trial

External Links

• MDCalc: Wells' Criteria
• Pulmonary Embolism Video

Review Questions

1 The utility of a quantitative D-dimer test is greatest in which of the following patients suspected of a pulmonary embolism?

	Patients with a low pre-test probability
	Patients with an intermediate pre-test probability
	Patients with a high pre-test probability

2 In which of the following patients can a negative CT pulmonary angiogram (alone) exclude the diagnosis of PE?

	A patient with low pretest probability who required additional diagnostic testing because of a positive D-dimer
	A patient with an intermediate pretest probability with a negative CT pulmonary angiogram in whom you are still concermed for PE
	A patient with an intermediate pretest probability with a negative d-dimer and a negative CT pulmonary angiogram
	Neither of the above

3 When would venous ultrasound be indicated as the initial imaging modality when you are evaluating a person with symptoms consistent with PE?

	Patients with obvious signs of DVT for whom venous ultrasound is readily available
	Patients with borderline renal insufficiency
	Patients with CT contrast agent allergy
	Pregnant patient
	All of the above