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Objective: The incidence of tuberculosis worldwide has emphasized the need for better assays designed to diagnose the disease, principally the extrapulmonary form. The objective of the present study was to validate the performance of an automated method for the determination of adenosine deaminase (ADA) activity in pleural fluid (PF) and cerebrospinal fluid (CSF), comparing it with a conventional method (the modified Giusti method)., Methods: In total, 134 samples were selected from among those tested in our laboratory: 94 PF samples and 40 CSF samples. The ADA activity was determined using the two methods. Inter- and intra-assay precision was determined, linear regression analysis was performed, simple concordance tests were conducted, and the means of the differences were calculated., Results: The correlation coefficients for PF and CSF samples were, respectively, 0.96 and 0.95. Inter-assay precision was determined using 21 replicates at 3 different activity levels: low, medium and high. The percentage coefficient of variation (%CV) was, respectively, 5.9, 8.1 and 5.8 for PF samples, compared with 21.9, 18.6 and 13.8 for CSF samples. Intra-assay precision in %CV was 1.3 and 11.7, respectively, for PF and CSF samples. The concordance between the methods in PF and CRF samples was, respectively, 96.8% and 100%, considering the reference values for the diagnosis of TB to be 40 U/L (conventional) and 30 U/L (automated) in PF samples, versus 9 U/L (for both methods) in CSF samples., Conclusions: The results validate the use of the automated method of determining ADA activity in PF and CSF samples as an alternative to the conventional method.

Objective: To evaluate Brazilian studies by summarizing the accuracy of adenosine deaminase in the diagnosis of pleural tuberculosis, with the objective of lending support to the movement to make the test part of the routine investigation of pleural effusions., Methods: A search for Brazilian studies related to the determination of adenosine deaminase levels in the pleural liquid was carried out. These studies were evaluated and included in this study. The data were analyzed using summary receiver operating characteristic (SROC) curves, which enabled the studies to be collected and evaluated regarding the accuracy of the diagnosis. As for the global values of sensitivity and specificity, the Bayes' theorem was applied to calculate the post-test probabilities in different prevalences of the disease., Results: Twenty-five studies dating from 1987 to 2005 and including enough information to be used in the meta-analysis were identified. After evaluation, nine studies were included, totaling 1674 patients. According to the SROC curve, a sensitivity of 91.8% (95% CI: 89.8-93.6%) and a specificity of 88.4% (95% CI: 86.0-90.5%) were found, with an area of 0.969 below the curve. The overall odds ratio was 112.0 (95% CI: 51.6-243.2). Considering a prevalence of tuberculosis of 50% (considered neutral), the post-test probability was 88.7% for a positive test and 91.5% for a negative test., Conclusions: Despite the differences found among studies, it is possible to conclude that the determination of adenosine deaminase levels has high accuracy in the diagnosis of the pleural tuberculosis and should be used as a routine test in its investigation.

Adenosine deaminase is an enzyme that actively participates in the metabolism of the adenine nucleotides. It catalyzes the irreversible hydrolytic deamination of deoxyadenosine and adenosine with the production of deoxyinosine and inosine respectively and of ammonia. This enzyme thus plays an important role in lympho-monocyte maturation and activation. The increase in its activity in different biological fluids (pleural, pericardial, peritoneal, intra-articular and cerebrospinal fluids) has been used as a rapid diagnostic test in tuberculosis infection. In human immunodeficiency virus infection, it was verified that enzymatic activity progressively increases in serum and blood cells, accompanying the natural evolution of the disease. The physiopathological mechanism has not been definitely established but the CD4+ lymphocytes and macrophages are pointed to as being accountable for the enzyme's increase in activity. For this reason, adenosine deaminase could be a marker of the cellular immune response. The study of adenosine deaminase activity in blood cells elucidated the diagnosis of severe combined immunodeficiency (due to a congenital lack of the enzyme) in 30 to 50% of the cases. One type of congenital hemolytic anemia is due to an exaggerated enzymatic activity in red blood cells.