Clinical diagnostic utility of adenosine deaminase, interferon-γ, interferon-γ-induced protein of 10 kDa, and dipeptidyl peptidase 4 levels in tuberculous pleural effusions.

OBJECTIVE: Current tools for the diagnosis of tuberculous pleural effusions are suboptimal. The study was undertaken to evaluate the accuracy of pleural fluid adenosine deaminase (ADA), interferon (IFN)-γ, interferon-γ-induced protein of 10 kDa (IP-10), and dipeptidyl peptidase (DPP) 4 levels in differentiating tuberculous pleural effusion (TPE) and non-TPE.

METHODS: A total of 122 samples of pleural effusion were studied. Pleural fluid ADA activity was measured with the colorimetric method, and IP-10, IFN-γ, and DPP4 levels were measured with enzyme-linked immunosorbent assay.

RESULTS: ADA activity and IP-10, IFN-γ, and DPP4 levels were significantly higher in TPE than in non-TPE (88.9 ± 62.7 U/L vs 18.1 ± 16.2 U/L, P < .05; 147.5 ± 117.3 ng/L vs 24.9 ± 19.7 ng/L, P < .05; 627.2 ± 345.3 ng/L vs 152.6 ± 71.4 ng/L, P < .05; and 560.6 ± 451.2 vs 56.8 ± 57.7, P < .05, respectively). The diagnostic sensitivity and specificity of ADA activity (cutoff value of 40 U/L) were 93.6% and 90.9%, respectively, and higher than those of IFN-γ (91.0% and 88.6% at the cutoff value of 225 ng/L, respectively), DPP4 (88.5% and 81.8% at the cutoff value of 75 ng/L, respectively), and IP-10 (83.3% and 86.4% at the cutoff value of 44 ng/L, respectively).

CONCLUSION: The roles of ADA and IFN-γ in the differential diagnosis of tuberculous pleurisy are pivotal. ADA or IFN-γ in combination with DPP4 or IP-10 can aid in differentiation between TPE and non-TPE with improved specificity and diagnostic efficiency.