TNF-а, among other cytokines, initiates a wide spectrum of biological activities that help activate the host’s response to infection, and thus may play pathophysiologic roles in PPE. Odeh et al measured serum and pleural fluid TNF-а in 13 patients with UPPE and 8 patients with nonempyemic CPPE. At an optimal cutoff point of 10.7 pg/mL, discriminative properties for pleural TNF-а were as follows: sensitivity, 87.5%; specificity, 92.3%; and accuracy, 90.5% (AUC was not calculated). These statistics were all 100% for the P/S TNF-а ratio set at 3.0. By using a cutoff value of 80 pg/mL, we observed that the sensitivity of TNF-a (78%) to identify CPPE was double that of either pH (41%) or glucose (39%), whereas the specificity of the former (89%) was somewhat lower than those of the latter (94% and 97%, respectively). The combination of TNF-a and LDH increased the sensitivity to 91%, at the expense of a diminished specificity (77%).
Nevertheless, some degree of misclassification cost, ie, to place some unnecessary chest tubes, is acceptable from the clinical standpoint. Finally, unlike other research-ers who found a significant correlation between levels of pleural TNF-a and neutrophil counts in both UPPE (r = 0.44, p = 0.04) and CPPE (r = 0.57, p = 0.03), we did not observe such an association. This suggests that factors other than neutrophils account for the TNF-a concentrations in pleural fluid.
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