The differential diagnosis of tuberculous and malignant pleural effusion (PE) is extremely difficult and continues to pose clinical challenges. Aim of the study: To evaluate the utility of pleural fluid interferon gamma (IFN-c), tumor necrosis factor-alpha (TNF-a), adenosine deaminase (ADA) levels with T cells subsets in differential diagnosis of malignant (MPE) and tuberculous pleural effusions (TPE).

Methods: Forty patients with pleural effusion (20 tuberculous and 20 malignant) were included in the study. The percentages of CD3+ lymphocytes, CD4+ lymphocytes and Treg (CD4+ CD25+) cells in pleural effusion from patients with tuberculous and malignant PE were determined by flow cytometry. The concentrations of IFN-c, TNF-a, and ADA were simultaneously determined in pleural fluids by enzyme linked immunosorbent assay and colorimetric methods.

Results: IFN-c, TNF-a and ADA concentrations were significantly higher in TPE than MPE (2.26 ± 1.62 vs. 0.3 ± 0.20 IU/ml: P < 0.0001, 122.45 ± 47.69 vs. 35.03 ± 31.88 pg/ml: P < 0.0001 and 84.22 ± 41.47 vs. 23.19 ± 17.93 U/l: P < 0.0001 respectively). T-cells markers (CD3+ T-cells, CD4+ T-cells and T reg cells) were significantly higher in TPE than MPE (76.46% vs. 65.29%; P 0.004, 51.21% vs. 43.50%; P 0.044 and 14.60% vs. 12.43%; P 0.032 respectively).

CD3+ plus CD4+ as well as CD3+ plus CD4+ plus T reg combinations were all 100% specific for discriminating TPE from MPE. TNF-a plus IFN-c, TNF-a plus ADA, as well as IFN-c plus TNF-a plus ADA, were 100% specific for discriminating TPE from MPE. Furthermore, the specificity of combined-diagnostic value of IFN-c, TNF-a and ADA with T cells subsets was >95%. Conclusions: The combinations of pleural fluid IFN-c, TNF-a and ADA levels and T cells subsets could effectively address the challenge of distinguishing tuberculous pleural effusion from malignant pleural effusion.