The Wells' Criteria for Pulmonary Embolism is a clinical prediction rule that stratifies patients with suspected pulmonary embolism (PE) into different risk categories. It is used in the emergency department or outpatient setting to determine the likelihood of PE in patients presenting with symptoms such as shortness of breath, chest pain, or unexplained cough. 

The Wells' Criteria includes factors such as clinical signs and symptoms of deep vein thrombosis (DVT), an alternative diagnosis less likely than a PE, heart rate over 100 beats per minute, immobilization or surgery in the previous four weeks, previous history of DVT or PE, hemoptysis, and malignancy. 

The score helps clinicians decide whether to proceed with further diagnostic testing, such as D-dimer testing or computed tomography pulmonary angiography (CTPA). Patients are classified as having a low, moderate, or high probability of PE based on their total score.

The Wells' Criteria should not be used in patients with a clear alternative diagnosis, or in patients who have been on full anticoagulation for more than 48 hours. It is also not applicable in pregnant patients or in patients under the age of 18.

Wells' criteria for pulmonary embolism

# Criteria
 A. Clinical signs and symptoms of deep venous thrombosis (+3)
B. Previous, objectively diagnosed pulmonary embolism or deep venous thrombosis (+1.5)
C. Heart rate > 100 (+1.5)
D. Immobilization >= 3 days or surgery in the previous 4 weeks (+1.5)
E. Pulmonary embolism as likely as or more likely than an alternative diagnosis (+3)
F. Hemoptysis (+1)
G. Cancer/palliative care/stopped treatment of cancer within 6 months (+1)

# Conditions
- score <= 2
- score <= 6
- score > 6
- score == 0

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.