Light’s criteria Calculator
A calculator to distinguish whether Pleural effusion is Transudate or Exudate.
📋 Light’s criteria (Exudate if any one of the 3 criteria is met)
- Pleural fluid Protein / Serum Protein ratio ≥ 0.5
- Pleural fluid LDH / Serum LDH ratio ≥ 0.6
- Pleural fluid LDH ≥ Serum LDH ULN × 2/3
Additional criteria: If Protein difference > 3.1 g/dL or Albumin difference > 1.2 g/dL, Transudate is possible
⚠️ Caution: The above content is not an absolute standard. The cause of pleural effusion should be judged comprehensively according to each clinical situation.
Light's criteria for differential diagnosis of pleural effusion

When using Light's criteria, there is a possibility of misdiagnosing transudate as exudate (up to 25%). If clinically judged as transudate, calculate the difference between pleural fluid and blood protein and albumin. If each is greater than 3.1g/dL and 1.2g/dL respectively, it can be judged as transudate.
- Pleural fluid Protein - Blood Protein > 3.1g/dL → High possibility of Transudate
- Pleural fluid Albumin - Blood Albumin > 1.2g/dL → High possibility of Transudate

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