Pleural fluid biomarkers: beyond the Light criteria.

Although distinguishing transudates from exudates through the Light criteria is still considered a pragmatic first step in the diagnostic work-up of pleural effusions, the measurement of various pleural fluid biomarkers may aid in the identification of common and specific entities, such as heart failure (natriuretic peptides), tuberculosis (adenosine deaminase), malignancy (mesothelin, fibulin-3, immunocytochemical stains), or bacterial pleural infections (C-reactive protein). The use of these biomarkers is currently encouraged as a routine diagnostic procedure.