Exudative Pleural Effusion Calculation, Table

 Lights Criteria Calculator

An online lights criteria and exudative pleural effusion calculation.

Protein Paramaters

LDH Parameters


Exudative Pleural Effusion

Lights criteria can be used to determine the type of a patients pleural effusion and thus its etiology.


The following diseases typically are exudative effusions, but in certain cases may be transudative:


Trapped lung


Constrictive pericarditis


Pulmonary embolism


Lights criteria are more sensitive than specific for exudative effusions.

Transudate vs Exudate Table

Transudate is produced through pressure filtration without capillary injury while exudate is inflammatory fluid leaking between cells.

Appearance Clear Cloudy
Specific gravity < 1.012 > 1.020
Protein content < 2.5 g/dL > 2.9 g/dL
fluid protein/ serum protein < 0.5 > 0.5
SAAG = Serum [albumin] - Effusion [albumin] > 1.2 g/dL < 1.2 g/dL
fluid LDH upper limit for serum < 0.6 or < 23 > 0.6 or > 23
Cholesterol content < 45 mg/dL > 45
Radiodensity on CT scan 2 to 15 HU 4 to 33 HU