Pulmonary Embolism - Diagnosis

Diagnosis

To diagnose pulmonary embolism, medical societies recommend a review of clinical criteria to determine the need for testing, followed by testing to determine a likelihood of being able to confirm a diagnosis by imaging, followed by imaging if other tests have shown that there is a likelihood of a PE diagnosis.

The diagnosis of PE is based primarily on validated clinical criteria combined with selective testing because the typical clinical presentation (shortness of breath, chest pain) cannot be definitively differentiated from other causes of chest pain and shortness of breath. The decision to do medical imaging is usually based on clinical grounds, i.e. the medical history, symptoms and findings on physical examination, followed by an assessment of clinical probability.

The most commonly used method to predict clinical probability, the Wells score, is a clinical prediction rule, whose use is complicated by multiple versions being available. In 1995, Wells et al. initially developed a prediction rule (based on a literature search) to predict the likelihood of PE, based on clinical criteria. The prediction rule was revised in 1998 This prediction rule was further revised when simplified during a validation by Wells et al. in 2000. In the 2000 publication, Wells proposed two different scoring systems using cutoffs of 2 or 4 with the same prediction rule. In 2001, Wells published results using the more conservative cutoff of 2 to create three categories. An additional version, the "modified extended version", using the more recent cutoff of 2 but including findings from Wells's initial studies were proposed. Most recently, a further study reverted to Wells's earlier use of a cutoff of 4 points to create only two categories.

There are additional prediction rules for PE, such as the Geneva rule. More importantly, the use of any rule is associated with reduction in recurrent thromboembolism.

The Wells score:

• clinically suspected DVT — 3.0 points
• alternative diagnosis is less likely than PE — 3.0 points
• tachycardia (heart rate > 100) — 1.5 points
• immobilization (≥ 3d)/surgery in previous four weeks — 1.5 points
• history of DVT or PE — 1.5 points
• hemoptysis — 1.0 points
• malignancy (with treatment within 6 months) or palliative — 1.0 points

Traditional interpretation

• Score >6.0 — High (probability 59% based on pooled data)
• Score 2.0 to 6.0 — Moderate (probability 29% based on pooled data)
• Score <2.0 — Low (probability 15% based on pooled data)

Alternative interpretation

• Score > 4 — PE likely. Consider diagnostic imaging.
• Score 4 or less — PE unlikely. Consider D-dimer to rule out PE.