Wells score (pulmonary embolism)
Estimates probability of pulmonary embolism
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The Wells score is a clinical prediction rule used to classify patients suspected of having pulmonary embolism (PE) into risk groups by quantifying the pre-test probability. It is different than Wells score for DVT (deep vein thrombosis). It was originally described by Wells et al. in 1998,[1] using their experience from creating Wells score for DVT in 1995.[2] Today, there are multiple (revised or simplified) versions of the rule, which may lead to ambiguity.[1][3][4]
The purpose of the rule is to select the best method of investigation (e.g. D-dimer testing, CT angiography) for ruling in or ruling out the diagnosis of PE, and to improve the interpretation and accuracy of subsequent testing, based on a Bayesian framework for the probability of the diagnosis.
The rule is more objective than clinician gestalt, but still includes subjective opinion (unlike e.g. Geneva score).
External links
- Wells Score PE Calculator – Free online calculator for clinical use
Original algorithm
Source:[1]
Originally it was developed in 1998 to improve the low specificity of V/Q scan results (which then had a more important role in the workup of PE than now).
It categorized patients into 3 categories: low / moderate / high probability. It was formulated in the form of an algorithm, not a score.
Subsequent testing choices were V/Q scanning, pulmonary angiography, and serial compression ultrasound.
Revised score
The emergence of rapid D-dimer assays in 1995[5] prompted revision of the rule. The D-dimer assay and the revised Wells score can be combined to identify a population with a pre-test probability of PE of less than 2%.[6]
This version was published as a score, and according to the final score, patients could be categorized in either 3 groups (low / intermediate / high risk) or 2 groups (PE unlikely/ PE likely).
Subsequent testing choices included D-dimer testing for low risk cases to further understand the pre-test probability; and V/Q scanning, pulmonary angiography, and compression ultrasonography for intermediate / high risk patients and low-risk patients with positive D-dimer results.
| Variable | Points |
|---|---|
| Clinical signs and symptoms of DVT | 3 |
| An alternate diagnosis is less likely than PE | 3 |
| Heart rate >100 | 1.5 |
| Immobilization or surgery in the previous 4 weeks | 1.5 |
| Previous DVT / PE | 1.5 |
| Hemoptysis | 1 |
| Malignancy (treatment currently, in the previous 6 months, or palliative) | 1 |
Risk of PE using 3 categories (data from the derivation group)
| Risk group | Points required | Risk of PE |
|---|---|---|
| Low risk | 0-1 | 3.6% |
| Moderate risk | 2-6 | 20.5% |
| High risk | >6 | 66.7% |
Risk of PE using 2 categories (data from the derivation group)
| Risk group | Points required | Risk of PE |
|---|---|---|
| Low | 0-4 | 5.1% |
| High | >4 | 39.1% |