ToolsCalculators
Light's Criteria for Exudative Effusions
Distinguishes exudative from transudative pleural effusions using paired fluid and serum chemistries.
Light's Criteria for Exudative Effusions
Pleural fluid protein
g/dL
Serum protein
g/dL
Pleural fluid LDH
U/L
Serum LDH
U/L
Upper limit of normal for serum LDH (assay-specific)
U/L
Complete the fields above to see the result.
When to use
- Classifying a new pleural effusion as exudative or transudative to direct the differential diagnosis and further work-up.
Formula
Exudate if any one of: pleural/serum protein >0.5; pleural/serum LDH >0.6; pleural LDH > 2/3 the assay's upper limit of normal for serum LDH.
Pearls and pitfalls
- Sensitivity for exudates is very high (~98%), but roughly 25% of transudates are misclassified as exudates, especially in patients on diuretics — consider serum-to-pleural albumin gradient if the clinical picture is discordant.