Tumor necrosis factor-alpha in pleural fluid - A marker of complicated parapneumonic effusions

Study objectives: We sought to determine whether pleural fluid tumor necrosis factor (TNF)-alpha is a more accurate parameter to identify nonpurulent complicated parapneumonic effusion (CPPE) than the classical chemistries, namely pH, glucose, or lactate dehydrogenase (LDH). Methods: We studied 80 consecutive patients with parapneumonic effusions (35 with uncomplicated parapneumonic effusion [UPPE], 23 with nonpurulent CPPE, and 22 with empyema). Concentrations of standard biochemical parameters together with TNF-alpha were measured in pleural fluid, the latter by using an immunoenzymometric assay. Results: Pleural TNF-alpha was significantly higher in CPPE (133.0 pg/mL) and empyema (142.2 pg/mL) than in UPPE (39.1 pg/mL). A cut-off value of 80 pg/mL for pleural TNF-alpha resulted in a sensitivity, specificity, and area under receiver operating characteristic curve (AUC) of 78%, 89%, and 0.87, respectively, for the diagnosis of nonpurulent CPPE. A multivariate analysis selected both pleural TNF-alpha greater than or equal to 80 pg/mL and LDH greater than or equal to 1,000 U/L (sensitivity, 74%; AUC = 0.86), but excluded pleural glucose less than or equal to 60 mg/dL (sensitivity, 39%; AUC = 0.82) and pH less than or equal to 7.20 (sensitivity, 41%; AUC = 0.78), for identifying the need for drainage. The combined sensitivity of pleural fluid TNF-alpha and LDH was found to be 91%. Conclusions: Pleural TNF-alpha may contribute to the identification of patients with nonpurulent CPPE with at least the same diagnostic accuracy, if not better, than the use of pH, glucose, or LDH.