Clinical tool
Wells PE
Pre-test probability for pulmonary embolism.
Score
0/ 12.5
Low probability
Roughly 1–3% prevalence of PE in this group. Consider PERC; if PERC-negative no further testing is generally needed, otherwise D-dimer.
Two-tier interpretation
PE unlikely — Score ≤ 4. D-dimer is appropriate; if negative, PE is excluded.
Wells estimates pre-test probability — it does not diagnose or exclude PE by itself, and its value lies entirely in deciding what to do next. The “alternative diagnosis” item is subjective and is the main source of variation between clinicians. Note that D-dimer is unreliable in pregnancy, recent surgery, malignancy and the elderly; age-adjusted thresholds improve specificity in patients over 50. A haemodynamically unstable patient with suspected PE should not be scored — resuscitate and image immediately.
For practising medics only. Clinical tools support judgement, they do not replace it. Always verify results against current guidelines and the patient in front of you.