CDR Blog

The Wells Criteria for PE is used as a risk stratification tool for pulmonary embolism. The tool assigns points to clinical features and risk factors of PE, including clinical symptoms of DVT, other diagnoses less likely than PE, tachycardia, immobilization or surgery in the last four weeks, previous DVT/PE, hemoptysis, and malignancy. Individuals are then stratified to be low risk (Wells <2), moderate risk (Wells 2-6), and high risk (Wells >6).

The criteria were identified and validated through logistic regression analysis involving a population of 1260 patients with suspected PE (Wells et al., 2000). These seven statistically significant predictors of PE were identified out of 40 potential variables. In patients determined to be PE unlikely (Wells ≤4) and with negative D-dimer, the rate of PE was 2.2% (95% CI, 1.0%-4.0%) in the derivation set and 1.7% (95% CI, 0.2%-6.0%) in the validation set. In patients with a low pretest probability of PE (Wells <2) and a negative D-dimer, only 1.5% (95% CI, 0.4%-3.7%) and 2.7% (95% CI, 0.3%-9.0%) of patients had a PE, respectively. The initial validation study concludes that using Wells in combination with D-dimer may safely exclude PE. They also note that when Wells >6, the utility of a negative D-dimer is limited.

Subsequent validation studies have found the prevalence of confirmed PE in those deemed “PE likely” or “high-risk” to be consistent. ​Wells et al. (2001) found the negative predictive value of using Wells for PE with a D-dimer to be ​99.5% (CI, 99.1% to 100%). Kaasjager et al. (2006) validated a simplified Wells Criteria, stratifying between Wells ≤4 and Wells >4. The authors found a statistically significant difference in prevalence between the two groups and the prevalence of VTE in patients with low Wells and negative D-dimer was ​0.5% (95% CI, 0.2%-1.1%).

Inter-rater reliability was of particular interest given that three points are given to a criterion based on clinician gestalt. A study by Wolf et al. (2004) concluded that the dichotomous model of the rule has a higher degree of interrater reliability compared to the trichotomous model, but that agreement was independent of the level of training of the provider.

In terms of impact, a retrospective study by Stojanovska et al. (2015) showed that there is potential for the rule to safely reduce the use of CTPA. They found 45% of CTPA to be inappropriate given the CDRs indicating PE unlikely. Limitations of this study include that it was conducted in a cancer center with higher prevalence of PE, higher proportion of missed cases, and decreased utility of D-dimer. Despite this potential to reduce CTPA use, Geeting et al. (2016) did not find a change in clinical practice in their prospective study pre and post implementation of a mandatory Wells score before CTPA. Interestingly, they found an increase in frequency of the “other diagnoses less likely than PE” criterion over time. The barrier to impact appears to be the heavy influence of the subjective criterion, which would then warrant further imaging.

In our appraisal of the evidence, using the guidelines by McGinn et al. (2000), we rate the Wells Criteria for PE to be a ​Level 2 Clinical Decision Rule. ​The Criteria can be used in various settings with accuracy, but it has limited impact on clinician behaviours. Both dichotomous and trichotomous variations of the rule have been validated in both in- and out-patient populations to determine the pre-test probability of PE. In clinical practice, the Criteria are used in conjunction with other clinical tools, such as PERC and D-dimer, as recommended on UpToDate (​Thompson, Kabrhel, & Pena, 2020).

1. Geeting, G. K., Beck, M., Bruno, M. A., Mahraj, R. P., Caputo, G., DeFlitch, C., & Hollenbeak, C. S. (2016). Mandatory Assignment of Modified Wells Score Before CT Angiography for Pulmonary Embolism Fails to Improve Utilization or Percentage of Positive Cases. AJR. ​American Journal of Roentgenology, 207​(2), 442–449. ​https://doi.org/10.2214/AJR.15.15394

2. Kaasjager, K., Kamphuisen, P. W., Kramer, M. H. H., Kruip, M. J. H. A., Kwakkel-van, J. M., Erp, F. W. G., ... & Tick, L. W. (2006). Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing and computed tomography. JAMA, 295​(2), 172-179.

3. McGinn, T. G., Guyatt, G. H., Wyer, P. C., Naylor, C. D., Stiell, I. G., & Richardson, W. S. (2000). Users' guides to the medical literature: XXII: how to use articles about clinical decision rules. Evidence-Based Medicine Working Group. ​JAMA, 284(​ 1), 79–84. https://doi.org/10.1001/jama.284.1.79

4. Thompson, B.T., Kabrhel, C., Pena, C. (2020, June 30). ​Clinical presentation, evaluation, and diagnosis of the nonpregnant adult with suspected acute pulmonary embolism.​ UpToDate. Retrieved October 9, 2020, from https://www.uptodate.com/contents/clinical-presentation-evaluation-and-diagnosis-of-the-nonpre gnant-adult-with-suspected-acute-pulmonary-embolism

5. Wells, P. S., Anderson, D. R., Rodger, M., Ginsberg, J. S., Kearon, C., Gent, M., Turpie, A. G., Bormanis, J., Weitz, J., Chamberlain, M., Bowie, D., Barnes, D., & Hirsh, J. (2000). Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer. ​Thrombosis and Haemostasis, 83​(3), 416–420.

6. Wells, P. S., Anderson, D. R., Rodger, M., Stiell, I., Dreyer, J. F., Barnes, D., Forgie, M., Kovacs, G., Ward, J., & Kovacs, M. J. (2001). 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. ​Annals of Internal Medicine, 135(​ 2), 98–107. ​https://doi.org/10.7326/0003-4819-135-2-200107170-00010