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Calculate Wells' clinical probability score for Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), stratifying low, moderate, and high clinical risk tiers.
Frequently Asked Questions
What is Wells' Criteria used for in emergency medicine?
Wells' Criteria is a validated clinical prediction rule used to estimate the pre-test probability of Pulmonary Embolism (PE) or Deep Vein Thrombosis (DVT), guiding whether a D-dimer blood test or immediate imaging (CTPA or venous duplex ultrasound) is appropriate.
How does the two-tier vs three-tier Wells model work for PE?
In the two-tier model, a score of 4.0 or lower indicates PE is 'unlikely' (proceed with D-dimer). A score greater than 4.0 indicates PE is 'likely' (proceed straight to CT pulmonary angiogram). In the three-tier model, scores are categorized as Low (<2), Moderate (2-6), and High (>6).
What is the age-adjusted D-dimer cutoff for ruling out PE/DVT?
For patients older than 50 years, the age-adjusted D-dimer cutoff equals Age x 10 ng/mL FEU (e.g., a 70-year-old has a cutoff of 700 ng/mL instead of 500 ng/mL), safely reducing unnecessary CT scans without missing embolisms.
Why does an alternative diagnosis subtract 2 points in Wells' DVT criteria?
If an alternative clinical condition (such as cellulitis, Baker's cyst, superficial thrombophlebitis, or calf muscle tear) is at least as likely as DVT, 2 points are subtracted because clinical signs are easily confounded by non-thrombotic lower leg swelling.