Gas chromatographically quantitated lactate in empyema and other pleural effusions.

To determine the value of gas chromatographically measured lactate in distinguishing between empyema and other causes of pleural effusion, consecutively collected samples of pleural fluid were studied. In 15 cases of empyema the mean lactate concentration was 11.60 mM and higher than in 41 patients with other diagnoses (mean 3.98 mM). The concentration of lactate remained unchanged during storage at 4 degrees C for two years. Gas chromatographic quantitation of lactate is useful in the presumptive diagnosis of empyema, and stability of the lactate concentration allows retrospective analyses.