# Wells' Criteria for Pulmonary Embolism Calculator
> Free Wells' Criteria calculator for pulmonary embolism pre-test probability. Two-tier and three-tier bands. Based on Wells 2000 + ACCP/ESC PE guidelines. Clinician decision support.

## Overview

The Wells' Criteria for Pulmonary Embolism stratifies pre-test probability of PE in adults with suspected acute PE. The original score totals 0–12.5 across seven items: clinical signs of DVT, PE as the most likely diagnosis, heart rate over 100, immobilisation or recent surgery, prior PE/DVT, haemoptysis, and active malignancy. The two-tier interpretation (≤ 4 vs > 4) drives whether D-dimer or imaging is the next reasonable step in many algorithms; the three-tier interpretation segments low, moderate, and high probability. The ACCP and ESC PE guidelines reference Wells' Criteria as a validated pre-test probability tool when paired with age-adjusted D-dimer.

## Who this is for

- Emergency physicians evaluating chest pain and dyspnoea
- Internal medicine residents on inpatient PE workups
- APPs in urgent care and acute care settings

## How to interpret the result

| Score / band | Meaning |
|---|---|
| Two-tier ≤ 4 | PE unlikely — D-dimer is commonly the next step (age-adjusted thresholds where applicable). |
| Two-tier > 4 | PE likely — CT pulmonary angiography or V/Q is commonly the next step. |
| Three-tier < 2 | Low probability. |
| Three-tier 2–6 | Moderate probability. |
| Three-tier > 6 | High probability — proceed to imaging. |

## Cited source

**ESC 2019 Guidelines for the Diagnosis and Management of Acute Pulmonary Embolism** (2019) — European Society of Cardiology

_Primary publication:_ Wells PS et al., Thromb Haemost 2000 (original Wells' Criteria)

## FAQs

### Should I use the two-tier or three-tier Wells' interpretation?

Most modern algorithms (ACCP, ESC) use the two-tier interpretation: Wells ≤ 4 means PE unlikely (proceed to D-dimer), Wells > 4 means PE likely (proceed to CTPA). The three-tier version is older and still appears in some literature.

### Is age-adjusted D-dimer paired with Wells' Criteria?

Yes — when the two-tier Wells' score is ≤ 4 in patients > 50, an age-adjusted D-dimer (age × 10 ng/mL) is widely used to safely rule out PE without imaging. Verify against your institutional protocol.

### How does Wells' compare to PERC?

PERC is a rule-out tool used in low-risk patients (Wells' score ≤ 4 or gestalt low) to obviate D-dimer entirely if all eight criteria are negative. They are sequential, not interchangeable.

### Does Wells' apply to pregnancy?

Wells' Criteria has limited validation in pregnancy. Pregnancy-specific algorithms (e.g. YEARS-pregnancy, Geneva) and obstetric input are commonly preferred. Always verify against current obstetric and pulmonary guidelines.

### Is a low Wells' score safe to discharge without imaging?

Wells' is a decision-support tool, not a discharge criterion. A low Wells' plus negative D-dimer (or PERC negative) supports a low post-test probability; the disposition decision still belongs to the clinician.

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_Rounds AI is a citation-first clinical AI assistant. It supports clinical reasoning by surfacing cited information and is not a substitute for independent clinical judgement._