Wells Criteria For Pulmonary Embolism
Stratifies pulmonary embolism risk before invasive testing or CT angiography take place.
In the text below the calculator there is more information on the criteria used and on how the result is interpreted.
The Wells criteria stratifies the risk for a patient to suffer from pulmonary embolism (PE) and avoids unnecessary testing in cases that are highly unlikely.
This is based on a model created by Wells et al. that associates pretest probability with D-dimer testing.
The criteria used refers to the major risk factors for PE, such as symptoms of DVT, family history of VTEs, tachycardia or recent long term immobilisation.
There following table introduces the two interpretations of the Wells criteria score:
| Two tier interpretation | Scores ≤4: PE unlikely Scores >4: PE diagnosis likely |
| Three tier interpretation | Scores <2: Less than 15% PE diagnosis chance Scores 2-6: 29% chance of PE diagnosis Scores >6: Over 59% chance of positive diagnosis |
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Wells criteria explained
This is a clinical prediction model that aims to improve the accuracy of pre-test screening for pulmonary embolism and to decrease incidence of unnecessary clinical imagery.
There are 7 parameters that are taken into account, all referring to risk factors for venous thromboembolism events:
| Wells criteria | Points if positive | Explanation |
| Clinical signs and symptoms of DVT | 3 | Symptoms of deep venous thrombosis such as unilateral swelling of one leg or pain |
| An alternative diagnosis is less likely than PE | 3 | For example, when other cardiovascular or pulmonary symptoms are present |
| Tachycardia present (heart rate >100 bpm) | 1.5 | Rapid heart beat may indicate an impairment in blood flow at arterial/venous level |
| Immobilization for the past 3 days or surgery previous month | 1.5 | Increases risk of blood clotting |
| History of DVT or PE | 1.5 | Relevant risk factor |
| Hemoptysis present | 1 | Generic symptom of PE, however, differential diagnosis may be required (with ventricular systolic heart failure, severe mitral stenosis and other conditions) |
| Malignancy in treatment or palliative | 1 | Relevant risk factor |
Score interpretation
There are two separate interpretations available for the Wells criteria.
■ The first one, the “two tier” sets a cut off at 4 points, where patients scoring above 4 are likely to de diagnosed with pulmonary embolism.
■ The second one, the “three tier” argues that patients scoring below 2 points, carry a probability of positive diagnosis of less than 15%, patients scoring between 2 and 6 carry a moderate risk of PE diagnosis of 29% whilst patients scoring above 6 points carry a risk of over 59%.
About the study
The original study was conducted by Wells et al. in 2001 on a cohort of 930 consecutive patients with suspected pulmonary embolism that presented to emergency departments of four tertiary care hospitals in Canada.
The study sought to bypass the limitations of classic diagnosis which involved complex and time consuming tests such as ventilation-perfusion lung scanning or D-dimer assay.
Firstly, a clinical model was used to determine patients' pretest probability of pulmonary embolism and then a D -dimer test was performed.
Patients with a high-probability ventilation-perfusion scan, an abnormal result on ultrasonography or pulmonary angiography, or a venous thromboembolic event during follow-up were diagnosed with pulmonary embolism. Patients for which PE was ruled out were followed up for 3 months for occurrence of any thromboembolic events.
The study concluded that managing patients for suspected PE on the basis of pretest probability and D -dimer result is an accurate screening method and can decrease the rate of unnecessary diagnostic imaging.
Pulmonary embolism guidelines
PE is a condition in which a blockage in the main artery of the lung or one of its branches takes place. This is caused by a particle, called embolism, which arrives via blood stream from a different region of the body, most often a blood clot due to deep venous thrombosis (DVT) in one of the veins of the leg.
The main PE risk factors include:
■ Convalescence (prolonged bed rest);
■ Family history of VTE, DVT or PE;
■ Personal occurrence of VTE or DVT;
■ Hormone substitution therapy.
Pulmonary embolism is one of the life threatening conditions that has certain marker signals but is also difficult to differentiate from a host of other conditions.
Symptoms that are sudden in onset include: dyspnea, chest pain, low blood oxygen saturation, increased heart beat, low blood pressure, fainting or loss of consciousness.
Diagnostic measures are based on clinical observation, laboratory tests (D-dimer test that evaluates the existence of fibrin degradation product from blood clot) and imaging (CT pulmonary angiography which shows the pulmonary arteries).
Original source
Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D, Forgie M, Kovacs G, Ward J, Kovacs MJ. 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. Ann Intern Med. 2001; 135(2):98-107.
Validation
Wolf SJ, McCubbin TR, Feldhaus KM, Faragher JP, Adcock DM. Prospective validation of Wells Criteria in the evaluation of patients with suspected pulmonary embolism. Ann Emerg Med. 2004; 44(5):503-10.
Other references
1. Wells PS, Anderson DR, Rodger M, et. al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer. Thromb Haemost. 2000; 83(3): 416-20.
2. Goldhaber SZ (2005). Pulmonary thromboembolism. In Kasper DL, Braunwald E, Fauci AS et al. Harrison's Principles of Internal Medicine (16th ed.). New York, NY: McGraw-Hill. pp.1561–65.
3. Van Belle A, Büller HR, Huisman MV, Huisman PM, Kaasjager K, Kamphuisen PW, Kramer MH, Kruip MJ, Kwakkel-van Erp JM, Leebeek FW, Nijkeuter M, Prins MH, Sohne M, Tick LW; Christopher Study Investigators. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172-9.
Specialty: Pulmonology
System: Respiratory
Objective: Predictor
Type: Criteria
No. Of Criteria: 7
Year Of Study: 2001
Article By: Denise Nedea
Published On: May 16, 2017 · 07:35 AM
Last Checked: May 16, 2017
Next Review: May 16, 2023