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

ObjectiveCurrent 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.MethodsA 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.ResultsADA 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).ConclusionThe 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.