Lit of the Week – Wells Score

Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D, Forgie M, Kovacs G, Ward J, Kovacs MJ. 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. Ann Intern Med. 2001 Jul 17;135(2):98-107.

Clinical question / background:

• Is there a simple clinical model to rule out pulmonary embolism in patients presenting to the emergency department?

Design:

• Prospective cohort study
• 930 participants in 4 Canadian Centers
• Inclusion: Adults with suspected PE with sxs < 30 days; chest pain or shortness of breath acute in onset
• Exclusion: UE DVT as likely source of PE, no sxs within 3 days of presentation, expected survival < 3 months, anticoagulation therapy for 24 hours or more, contraindication to contrast, pregnancy, < 18 y/o, unable to follow-up

Intervention:

• Implementation of clinical model to determine probability of PE
  • 3 points – Clinical Signs/Sxs of DVT
    • Objectively measured leg swelling and/or pain with palpation of deep veins
  • 1.5 points – Tachycardia (HR> 100)
  • 1.5 points – bed rest (except going to bathroom) for 72 hours, or surgery within previous 4 weeks
  • 1.5 points – prior dx of DVT or PE
  • 1 point – hemoptysis
  • 1 point – malignancy (current rx, palliative care, or treatment within the preceding 6 months)
  • 3 points – PE as most likely or as likely as alternative diagnosis based on physical exam and basic workup (EKG, CXR, screening labs)
• Pretest Probability of PE based on Score
  • < 2.0 points – low risk
  • 2.0 – 6.0 points – moderate risk
  • >6.0 points – high risk
• Primary Outcome
  • 3-month occurrence of PE based on initial risk stratification

• Algorithm (see below)

Results:

• LOW pre-test probability – PE diagnosed in 1.3% at 3-month f/u
• MODERATE pre-test probability – PE diagnosed in 16.2% at 3-month f/u
• HIGH pre-test probability – PE diagnosed in 37.5% at 3-month f/u

Take-home:

• The Wells’ Criteria risk stratifies patients for pulmonary embolism (PE) and provides an estimated pre-test probability. The physician can then chose what further testing is required for diagnosing pulmonary embolism (I.E. d-dimer or CT angiogram or V/Q

Strengths:

• Simple to use; clear cut-offs
• Validated multiple times in multiple settings since original paper

Weaknesses / Critiques

• Subjective component of PE being most likely diagnosis can push score to intermediate range and lead to unnecessary testing
• Reliance on d-dimer for decision-making

Follow-up / Real World Application

• If patient determined to be low Risk, consider d-dimer testing
• Also in low-risk patients, can be used with the PERC as rule-out for PE
  • The PERC rule can be applied to patients where the diagnosis of PE is being considered, but the patient is deemed low-risk. A patient deemed low-risk by physician’s gestalt who is also <50 years of age, with a pulse <100 bpm, SaO₂≥ 95%, no hemoptysis, no estrogen use, no history of surgery/trauma within 4 weeks, no prior PE/DVT and no present signs of DVT can be safely ruled out and does not require further workup
• In medium / high risk patients, consider CTA (+/- d-dimer) or V/Q

• Calculator links

• http://www.mdcalc.com/wells-criteria-for-pulmonary-embolism-pe/
• http://www.mdcalc.com/perc-rule-for-pulmonary-embolism/