Measurement of lactic acid in pleural fluid.

Lactic acid (LA) concentrations in the pleural fluid of 75 patients were determined by the Monotest Lactate Kit (MLK). Lactic acid values in 18 cases of bacterial or tuberculous pleural infection were strikingly higher (mean 81 mg%, range 45-200 mg%), than in 42 cases with pleural effusion due to congestive heart failure, hepatic cirrhosis, nephrosis, trauma, and systemic lupus erythematosus (SLE; mean 19 mg%, range 6-47 mg/). High levels of LA were also found in the pleural fluid of 15 patients with malignancy of pleural cavity. Determination of LA can be an additional rapid tool in the differentiation between bacterial pleural inflammation and pleural effusion of various forms except in cases with malignancy of the pleural cavity.