Frequently asked questions (FAQ)
What is the Wells score for pulmonary embolism (PE)?
The Wells score for PE is a clinical prediction rule developed by Philip Wells and colleagues to estimate the pretest probability of pulmonary embolism in adults with suspected PE. It sums 7 weighted clinical findings into a total of 0 to 12.5. The result guides the next diagnostic step — for example whether a D-dimer test is enough or CTPA imaging is needed right away. The score is educational, not a diagnosis.
What are the 7 Wells PE criteria and their weights?
The seven original criteria (Wells et al.): clinical signs/symptoms of DVT +3; PE judged equally likely or more likely than an alternative diagnosis +3; heart rate above 100/min +1.5; immobilization for at least 3 days or surgery within the last 4 weeks +1.5; previously objectively diagnosed DVT/PE +1.5; hemoptysis (coughing up blood) +1; malignancy on treatment, treated within the last 6 months, or palliative +1. Maximum total: 3+3+1.5+1.5+1.5+1+1 = 12.5.
How does a Wells score calculation work in practice?
Check each criterion present in the patient, then add up the weights. Example 1: a patient with a heart rate of 110/min (+1.5) and coughing up blood (+1) scores 2.5 — intermediate category in the 3-tier model, PE unlikely in the 2-tier model. Example 2: a patient with DVT signs (+3), PE judged most likely (+3), and a history of DVT (+1.5) scores 7.5 — high category in the 3-tier model and PE likely in the 2-tier model.
What is the difference between the 2-tier and 3-tier Wells models?
The original 3-tier model divides results into three categories: low (score below 2), intermediate (score 2 to 6), and high (score above 6). The simplified 2-tier model uses only two categories: PE unlikely (score 4 or less) and PE likely (score above 4). This calculator shows both models — use the toggle in the results panel to switch between them.
After getting a Wells score, what is the next diagnostic step?
It generally follows pretest probability: low category or PE unlikely — high-sensitivity D-dimer test; if negative, PE is ruled out without imaging; if positive, proceed to CTPA. Intermediate category — high-sensitivity D-dimer or straight to CTPA. High category or PE likely — go straight to CT pulmonary angiography (CTPA) or V/Q scan, because D-dimer is not reliable enough to rule out PE at high pretest probability. Testing decisions always rest with the physician treating the patient.
How does the Wells score for PE differ from the Wells score for DVT?
They are different rules from the same researcher — do not mix them up. The Wells score for PE uses 7 weighted criteria with a maximum total of 12.5. The Wells score for DVT uses entirely different criteria: 9 findings at +1 each and one criterion at −2 when an alternative diagnosis is equally likely. This calculator only computes the Wells score for pulmonary embolism (PE).
When should the Wells score not be used?
The Wells score was validated in hemodynamically stable adults with suspected PE, typically in the emergency department or outpatient setting. It is not validated for pregnant patients (a dedicated algorithm such as the pregnancy-adapted YEARS is used), patients already on therapeutic-dose anticoagulants, or unstable patients who need immediate imaging. If unsure whether the score applies, consult a physician.
How does the Wells score relate to the D-dimer test?
The Wells score determines pretest probability BEFORE D-dimer is checked — the order must not be reversed, because D-dimer interpretation depends on pretest probability. D-dimer is only useful for ruling out PE at low or intermediate pretest probability; at high probability, a negative D-dimer cannot be trusted. In patients over 50, the D-dimer cutoff can be age-adjusted (age × 10 µg/L FEU).
What are the PERC criteria and when are they used?
PERC (Pulmonary Embolism Rule-out Criteria) is an 8-item rule for ruling out PE without any D-dimer testing — but only in patients already assessed as very low risk, for example with a low-category Wells score. If even one of the 8 PERC criteria is positive (e.g. age 50 or older, heart rate 100/min or more), further testing such as D-dimer is still required.
How does the Wells score differ from the Geneva score?
Both estimate pretest PE probability, but with different approaches. The revised Geneva score uses fully objective criteria — age, VTE history, tiered heart rate, and leg findings — with no subjective assessment. The Wells score uses only 7 items and relies heavily on physician clinical judgment, especially the PE-more-likely-than-alternative-diagnosis criterion worth 3 points.
What is the PE prevalence in each Wells score category?
In the derivation cohort (Wells 2000): low category 3.6%, intermediate 20.5%, and high 66.7%. In the 2-tier model validation (Christopher study): PE unlikely 12.1% and PE likely 37.1%. These figures come from study populations and describe how often PE was found in each category — not a definite probability for one individual. Always interpret them together with the patient's clinical picture.
Does this calculator replace a physician's assessment?
No. This calculator is an educational aid for understanding how the Wells score works. One of its criteria — the judgment that PE is more likely than an alternative diagnosis — fundamentally requires direct clinical examination by a physician and cannot be self-assessed by a patient. Do not use the calculator results to decide treatment on your own; always consult a medical professional.