Mediators in pleural effusions of different origin: a two-step diagnostic study

Background: Many mediators in pleural effusions give diagnostic information. This study therefore aimed to find out whether the repeated determination of interleukin (IL)-6, IL-15, vascular endothelial growth factor (VEGF), and tissue inhibitors of metalloproteinase (TIMP)-2 would confirm previous results and, furthermore, whether a combination of these parameters could achieve a higher diagnostic yield. Methods: Two consecutive groups of patients with pleural effusions were included. The underlying disease entities in series I vs. series II were: 12 vs. 0 tuberculosis (TB), 19 vs. 30 primary lung cancer, 7 vs. 14 secondaries to the lung, 5 vs. 13 congestive heart failure, and 2 vs. 7 para-pneumonic effusion. Results: VEGF could not differentiate values of series I to the same degree as in series II. For IL-15, totally deviating levels were obtained in series II. IL-6, however, showed comparable results in both series. Values of TIMP-2 were generally higher in series II. The diagnostic accuracies of VEGF and IL-6 were comparable. With logistic regression, the data of VEGF and IL-6 could be used as a classifying tool when TB cases were excluded. The classifying tool based on the data of series I showed a high degree of diagnostic accuracy (area under the curve, AUC=0.94) in contrast to the calculation based on the data of series II (AUC=0.56). Combining both series, VEGF was superior. Conclusions: VEGF was confirmed as a valid marker for malignant diseases. VEGF in combination with IL-6 could serve as a classifying tool. TB cases, however, should be excluded. The previously proposed relevance of TIMP-2 as a diagnostic parameter could, similarly to IL-15, not be confirmed.