Wells score (pulmonary embolism)
The Wells score is a clinical prediction rule used to classify patients suspected of having pulmonary embolism into risk groups by quantifying the pre-test probability. It is different than Wells score for DVT. It was originally described by Wells et al. in 1998, using their experience from creating Wells score for DVT in 1995. Today, there are multiple versions of the rule, which may lead to ambiguity.
The purpose of the rule is to select the best method of investigation 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.
Original algorithm
Source:Originally it was developed in 1998 to improve the low specificity of V/Q scan results.
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
Sources:The emergence of rapid D-dimer assays in 1995 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%.
This version was published as a score, and according to the final score, patients could be categorized in either 3 groups or 2 groups.
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 | 1 |
Risk of PE using 3 categories
| 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