← Clinical Scores and Calculators
Light's Criteria
Differentiate exudative from transudative pleural effusions. Applied to pleural fluid obtained by thoracentesis.
Indication
- Differentiate exudative from transudative pleural effusions. Applied to pleural fluid obtained by thoracentesis.
Criteria
- id: fluid_protein; label: Pleural fluid protein (g/dL); type: number; placeholder: e.g. 4.0
- id: serum_protein; label: Serum protein (g/dL); type: number; placeholder: e.g. 7.0
- id: fluid_ldh; label: Pleural fluid LDH (U/L); type: number; placeholder: e.g. 250
- id: serum_ldh; label: Serum LDH (U/L); type: number; placeholder: e.g. 200
- id: uln_ldh; label: Upper limit of normal serum LDH (U/L); type: number; placeholder: e.g. 220
Clinical pearls
- Light's criteria misclassify ~25% of transudates as exudates in patients on diuretics — use serum-to-fluid albumin gradient (>1.2 = transudate)
- pH <7.2 in a parapneumonic effusion is the strongest indication for chest tube drainage
- Malignant effusions are exudates in >95% of cases
Source and review
- Light RW et al. Ann Intern Med 1972. Last reviewed: 2025-01-01