Pleural fluid lactate in pleural effusion.

Pleural fluid lactate (PFL) and blood lactate (BL) concentrations were simultaneously measured in samples from 46 patients with pleural effusion. PFL exceeded 6 mmol/l in all 15 patients with pyogenic bacterial pleurisy but in only 5 of the other 31 patients. We have found that a PFL-BL difference greater than or equal to 6 mmol/l has a sensitivity of 100% and a specificity of 93.8% in detecting pyogenic pleural effusions. Results are available within 1 h of sample collection, so that PFL-BL difference may become a useful aid in the early assessment of pleural effusions.