Light's Criteria (Pleural Effusion) — free guideline decision tool
Classify a pleural effusion as exudate or transudate with Light's criteria.
Open guideline tool →Guideline-based
Implements the decision logic from published clinical guidelines.
Runs in your browser
No installation. Enter the patient's values and get a guideline recommendation instantly.
Data stays local
Nothing is uploaded. Results are for licensed clinicians only.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Pleural fluid protein | 4 g/dL |
|---|---|
| Serum protein | 7 g/dL |
| Pleural fluid LDH | 300 U/L |
| Serum LDH | 200 U/L |
| Serum LDH upper limit of normal | 240 U/L |
→Effusion typeExudate
- Protein ratio > 0.5：0.57 ✓
- LDH ratio > 0.6：1.50 ✓
- Pleural LDH > ⅔ ULN：300 vs 160 ✓
Common questions
What is Light's Criteria (Pleural Effusion)?
Classify a pleural effusion as exudate or transudate with Light's criteria.
How is Light's Criteria (Pleural Effusion) calculated? What is the core formula?
Exudate if any: pleural/serum protein > 0.5, pleural/serum LDH > 0.6, or pleural LDH > ⅔ of the serum LDH upper limit of normal.
When is Light's Criteria (Pleural Effusion) used?
Direct the work-up of a pleural effusion.
What are the key clinical points for Light's Criteria (Pleural Effusion)?
Any one positive criterion = exudate. Very sensitive; can misclassify diuresed transudates. Use the albumin gradient if results are discordant with the clinical picture.
What are the limits and cautions when using Light's Criteria (Pleural Effusion)?
For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
How is Light's Criteria (Pleural Effusion) calculated in practice? Can you show a worked example?
Inputs: Pleural fluid protein 4 g/dL, Serum protein 7 g/dL, Pleural fluid LDH 300 U/L, Serum LDH 200 U/L, Serum LDH upper limit of normal 240 U/L → Result: Effusion type Exudate（Protein ratio > 0.5: 0.57 ✓, LDH ratio > 0.6: 1.50 ✓, Pleural LDH > ⅔ ULN: 300 vs 160 ✓）
Run Light's Criteria (Pleural Effusion) now
Classify a pleural effusion as exudate or transudate with Light's criteria.
Open guideline tool →For licensed clinicians. Not a substitute for clinical judgement.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.