We analysed the efficacy of pleural adenosine deaminase (ADA(p)) and the ADA1/ADA(p) ratio in the diagnosis of pleural tuberculosis in 103 pleural effusions, 27 of which were tuberculosis (TB) and 76 other diagnoses (non-TB). Smears, cultures and pleural biopsies were carried out in all cases, and were used for final diagnosis. The diagnostic yield of the parameters under study were as follows: smears/cultures of mycobacteria in fluid 11.1%/33.3%; biopsy 33.3%/51.8% and tuberculosis granulomas 85.1%. The levels of ADA(p) and ADA1/ADA(p) ratio in TB and non-TB groups showed very significant differences (P < 0.00001); in the TB group: ADA, 54.7 ± 23.5 IU and ADA1/ADA(p) 0.27 ± 0.08; in the non-TB group: ADA(p) 18.3 ± 43.2 IU and ADA1/ADA(p) 0.64 ± 0.14. The assay established ADA levels in pleural fluid ≥ 40 IU and an ADA1/ADA(p), ratio ≤ 0.42 as cut-off levels to identify individuals in the TB group, with a sensitivity of 88.8%/100%, a specificity of 92%/98.6%, a positive predictive value (PPV) of 80%/96.4%, a negative predictive value (NPV) of 95.8%/100% and an accuracy of 91.2%/99.02%. The ADA(p) levels in 27 patients with TB, showed close correlation with the number of monocyte macrophages (P = 0.001), but not with the number of lymphocytes (P = n.s.). The ADA1/ADA(p) ratio overcomes the limitations of ADA(p) (false positives and negatives), and is the most useful parameter for diagnosis on account of a high diagnostic yield, low cost and speed of the asssay for identifying a pleural tuberculosis diagnosis, when compared with traditional methods.
Pérez-Rodríguez, E., Pérez Walton, I. J., Sánchez Hernández, J. J., Pallarés, E., Rubi, J., Jiménez Castro, D., & Díaz Nuevo, G. (1999). ADA1/ADAp ratio in pleural tuberculosis: An excellent diagnostic parameter in pleural fluid. Respiratory Medicine, 93(11), 816–821. https://doi.org/10.1016/S0954-6111(99)90267-6