Calculate the Wells score for pulmonary embolism from seven clinical criteria, estimate PE probability, and check the age-adjusted D-dimer next step.
Wells Score for Pulmonary Embolism Formula
The Wells score adds points from seven clinical criteria. The standard version uses weighted points:
Wells Score = 3(DVT signs) + 3(PE most likely) + 1.5(HR over 100) + 1.5(immobilization or surgery) + 1.5(prior PE or DVT) + 1(hemoptysis) + 1(malignancy)
A term is added only when that criterion is present, so the standard score runs from 0 to 12.5. The simplified version gives 1 point to each of the same seven criteria, so it runs from 0 to 7.
- DVT signs: clinical signs and symptoms of deep vein thrombosis, at minimum leg swelling and pain on palpation of the deep veins (3 points).
- PE most likely: pulmonary embolism is the leading diagnosis, or at least as likely as any alternative (3 points).
- HR over 100: heart rate above 100 beats per minute (1.5 points).
- Immobilization or surgery: bed rest for at least 3 days, or surgery within the previous 4 weeks (1.5 points).
- Prior PE or DVT: a previous, objectively diagnosed pulmonary embolism or deep vein thrombosis (1.5 points).
- Hemoptysis: coughing up blood (1 point).
- Malignancy: active cancer treated within the past 6 months, or receiving palliative care (1 point).
The calculator adds the points you select and reads the total two ways. The three-tier model sorts the standard score into low, moderate, or high probability. The two-tier model collapses the score into “PE unlikely” or “PE likely” to decide whether you order a D-dimer or move straight to imaging. The simplified model reports only the two-tier result, which is useful when you want a fast bedside answer without tracking half-point weights.
Score Interpretation and PE Probability
The same total means different things depending on the model. Read a standard Wells score against the three-tier bands first:
| Standard score | Three-tier category | Approx. PE prevalence |
|---|---|---|
| Under 2 | Low probability | About 1 to 3% |
| 2 to 6 | Moderate probability | About 16% |
| Over 6 | High probability | About 38 to 40% |
The two-tier model draws a single line at 4 points: a score of 4 or less is PE unlikely, and a score above 4 is PE likely. In the simplified model that line sits at 1 point, so 0 to 1 is PE unlikely and 2 or more is PE likely. A “PE unlikely” result does not rule out a clot on its own. You still need a negative D-dimer to safely close the workup, and in older patients the D-dimer cutoff should rise with age.
The table below shows the age-adjusted D-dimer threshold the calculator applies in the PE-unlikely pathway. For anyone over 50, the cutoff is age times 10 in nanograms per milliliter (fibrinogen equivalent units), which reduces false positives without missing clots:
| Age | Age-adjusted D-dimer cutoff (FEU) |
|---|---|
| 50 or younger | 500 ng/mL (0.5 micrograms/mL) |
| 60 | 600 ng/mL |
| 70 | 700 ng/mL |
| 80 | 800 ng/mL |
| 90 | 900 ng/mL |
Turn on the optional D-dimer section in the calculator to combine your two-tier result with this threshold. When the score is PE unlikely and the D-dimer sits below the age-adjusted cutoff, the tool reports that PE can be considered excluded. When the D-dimer is at or above the cutoff, or the score is PE likely, it points you to CT pulmonary angiography.
Example Calculations
Example 1, standard model with D-dimer. A 72-year-old has a prior DVT (1.5) and a heart rate of 108 (1.5). No other criteria apply, so the standard score is 3. That falls in the moderate three-tier band, but the two-tier result is PE unlikely because 3 is 4 or less. The age-adjusted D-dimer cutoff at age 72 is 720 ng/mL. A D-dimer of 480 ng/mL is below 720, so PE can be considered excluded and no imaging is needed.
Example 2, simplified model, same patient. In the simplified version each criterion is worth 1 point, so the prior DVT (1) and heart rate over 100 (1) give a total of 2. Because 2 is at or above the cutoff of 2, the simplified model calls this PE likely, which would send the patient to imaging. The two models can disagree at the margins, which is why the standard weighted score is the one most guidelines pair with age-adjusted D-dimer.
Frequently Asked Questions
Does a low Wells score rule out pulmonary embolism? No. A low or “PE unlikely” score lowers the probability but does not exclude a clot by itself. You confirm exclusion by pairing that result with a D-dimer below the age-adjusted threshold. If the D-dimer is elevated, or the score is PE likely, the next step is CT pulmonary angiography.
What is the difference between the two-tier and three-tier Wells score? The three-tier model reports low, moderate, or high probability and is useful for describing overall risk. The two-tier model reports only PE unlikely or PE likely, using a cutoff of 4 points, and is designed to drive the yes-or-no decision to test or image. Both use the same seven criteria and the same point totals.
Should I use the standard or the simplified version? The standard weighted score is the original and the one most validation studies and guidelines rely on, especially when combined with age-adjusted D-dimer. The simplified version, with 1 point per criterion, is easier to score at the bedside and performs similarly in studies, but it only gives a two-tier answer. If the two versions disagree, treat the more cautious result as the one to act on and use clinical judgment.