Calculate Wells score and check PERC rule criteria for pulmonary embolism risk.
The Wells score stratifies pretest probability, which then determines whether a D-dimer or imaging pathway is used. PERC is only valid in patients already assessed as low risk and requires every criterion to be negative. Applying PERC to a patient who is not low risk invalidates the rule entirely, which is the most common misuse of it.
Wells Score / PERC Rule
Wells sums weighted criteria; PERC requires all eight criteria to be negative
This reproduces a published formula for educational and reference use only. It is not a diagnostic tool, does not account for individual clinical context, and must not be used to make or change treatment decisions. Clinical assessment by a qualified healthcare professional is always required. Suspected pulmonary embolism is a medical emergency. If you have chest pain, breathlessness or coughing blood, seek emergency care immediately. These scores are decision aids for clinicians working within local diagnostic protocols.
Wells sums weighted criteria; PERC requires all eight criteria to be negative The Wells score stratifies pretest probability, which then determines whether a D-dimer or imaging pathway is used. PERC is only valid in patients already assessed as low risk and requires every criterion to be negative.
Applying PERC to a patient who is not low risk invalidates the rule entirely, which is the most common misuse of it.
This calculator takes 6 inputs: Wells criteria present, excluding heart rate and cancer, Heart rate, Active malignancy, Age, Oxygen saturation, Other PERC criteria present. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.