Lights criteria

Light's criteria are used to differentiate between exudative and transudative pleural effusion by analyzing pleural fluid and serum. The criteria are as follows:

A pleural effusion is classified as exudative if at least one of the following conditions is met:

1. Pleural fluid protein/Serum protein ratio > 0.5

2. Pleural fluid lactate dehydrogenase (LDH)/Serum LDH ratio > 0.6

3. Pleural fluid LDH > two-thirds of the upper limit of normal (ULN) for serum LDH

If none of these criteria are met, the pleural effusion is classified as transudative.