Interleukin-1 beta in pleural fluids of different etiologies. Its role as inflammatory mediator in empyema.

STUDY OBJECTIVES: To measure interleukin-1 beta (IL-1 beta) levels in pleural effusions of different etiologies and their relationship with several pleural inflammatory parameters, and to verify whether IL-1 beta can be used as diagnostic marker in the differential diagnosis of pleural diseases. MATERIAL AND METHOD: One hundred two pleural effusions were analyzed using a monoclonal antibody enzyme-linked immunosorbent assay. Pleural fluids were classified as follows: transudates (n = 28), empyema (n = 14), parapneumonic (n = 13), tuberculous (n = 19), neoplastic (n = 17), and miscellaneous effusions (n = 11). RESULTS: IL-1 beta was above 200 pg/mL in all the patients with empyema but only in three patients with other etiologies. Two of those three had parapneumonic effusions and the remaining one had a tuberculous pleurisy with a previous bacterial empyema. No significant relationships were found between pleural effusion IL-1 beta levels and the different inflammatory parameters analyzed. As a diagnostic criterion for empyema, pleural IL-1 beta concentration greater than 200 pg/mL had a sensitivity of 100%, a specificity of 96%, and a positive and negative predictive value of 0.82 and 1, respectively. CONCLUSIONS: Our data suggest that IL-1 beta has a significant role in pyogenic infections of the pleural space but not in effusions of other etiologies. It could be used as a diagnostic marker of empyema.