Assay of pleural fluid interleukin-6, tumour necrosis factor-alpha and interferon-gamma in the diagnosis and outcome correlation of tuberculous effusion

AbstractObjective: To assess the usefulness of interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) in the diagnosis and prediction of outcome of pleural tuberculosis.Patients and methods: Pleural fluid from 32 TB and 34 non-TB patients was sent for assay of IL-6, TNF-α and IFN-γ. Clinical parameters at presentation and residual pleural scarring at completion of treatment were assessed for pleural TB cases.Results: The pleural fluid levels of IL-6, TNF-α and IFN-γ in TB patients were significantly higher than those with non-TB effusions (P values of <0.001, 0.018 and <0.001, respectively by independent t-test). Utility of these cytokines for diagnosis of pleural TB was evaluated using receiver operating characteristic (ROC) curve analysis. The cut-off values for IL-6, TNF-α and IFN-γ determined in this analysis were 4000, 4 and 60pg/ml respectively, and their sensitivity and specificity were 90.6% and 76.5%, 90.6% and 79.4%, 100% and 100%, respectively. The pretreatment pleural fluid IL-6 levels had a positive correlation with the number of febrile days after treatment (Pearson correlation test: r=0.60, P=0.009). A negative correlation was found between the percentage reduction in pleural fluid cytokines after 2 weeks treatment and the extent of residual pleural scarring (IL-6: r=–0.62, P=0.041; TNF-α: r=–0.65, P=0.030; IFN-γ: r=–0.83, P=0.002).Conclusion: Pleural fluid IL-6, TNF-α and IFN-γ assays are useful in the diagnosis of pleural TB. The initial IL-6 level correlates with the number of febrile days. The percentage change of cytokines after 2 weeks of treatment also helps to predict residual pleural scarring