Diagnostic Accuracy with Total Adenosine Deaminase as a Biomarker for Discriminating Pleural Transudates and Exudates in a Population-Based Cohort Study.

BACKGROUND: An initial step in the evaluation of patients with pleural effusion syndrome (PES) is to determine whether the pleural fluid is a transudate or an exudate. OBJECTIVES: To investigate total adenosine deaminase (ADA) as a biomarker to classify pleural transudates and exudates. METHODS: An assay of total ADA in pleural fluids (P-ADA) was observed using a commercial kit in a population-based cohort study. RESULTS: 157 pleural fluid samples were collected from untreated individuals with PES due to several causes. The cause most prevalent in transudate samples (21%, n = 33/157) was congestive heart failure (79%, 26/33) and that among exudate samples (71%, n = 124/157) was tuberculosis (28.0%, 44/124). There was no significant difference in the proportion of either sex between the transudate and exudate groups. The median values of P-ADA were significantly different (P < 0.0001) between both total exudates (18.4 U/L; IQR, 9.85-41.4) and exudates without pleural tuberculosis (11.0 U/L; IQR, 7.25-19.75) and transudates (6.85; IQR, 2.67-11.26). For exudates, the AUC was 0.820 (95% CI, 0.751-0.877; P < 0.001), with excellent discrimination. The optimum cut-off point in the ROC curve was determined as the level that provided the maximum positive likelihood ratio (PLR; 14.64; 95% CI, 2.11-101.9) and was22.0 U/L. For transudates, the AUC was 0.8245 (95% CI, 0.7470-0.9020; P < 0.0001). Internal validation of the AUC after 1000 resamples was evaluated with a tolerance minor than 2%. The clinical utility was equal to 92% (95% CI, 0.84 to 0.96, P < 0.05). CONCLUSIONS: P-ADA is a useful biomarker for distinguishing pleural exudates from transudates.

Evaluation of cerebrospinal fluid adenosine deaminase activity for the differential diagnosis of tuberculous and nontuberculous meningitis.

INTRODUCTION: The diagnosis value of adenosine deaminase (ADA) activity in cerebrospinal fluid (CSF) of tuberculous meningitis (TBM) has been well documented. However, the cutoff point of CSF ADA has not been fully assessed. In the current study, the authors set to calculate the cutoff points of ADA and monitor the changes of CSF ADA activities in patients with TBM after antitubercular therapy. METHODS: CSF ADA activity in patients with different types of meningitis was measured by Trinder enzyme-coupled assay. RESULTS: The mean CSF ADA values in the patients with TBM, bacterial meningitis, viral meningitis, cryptococcal meningitis and noninfectious neurologic disorders were 14.1 ± 5.4, 9.6 ± 5.5, 4.3 ± 2.5, 7.8 ± 3.4 and 2.6 ± 1.3 U/L, respectively. CSF ADA activity was significantly higher in TBM compared with patients with non-TBM (P < 0.05). Moreover, the best cutoff point for differentiating between TBM and non-TBM was 9.5 U/L. In addition, CSF ADA activity was decreased in patients with TBM after antitubercular therapy in a time-dependent manner. CONCLUSIONS: The determination of ADA with a cutoff value of 9.5 U/L in CSF is a useful aid for the differential diagnosis of TBM and non-TBM. Moreover, dynamic monitoring of CSF ADA activity may be an indicator for evaluating antitubercular therapy in TBM.

Optimization of adenosine deaminase assay by response surface methodology.

The effect of four variables (adenosine, glutamate dehydrogenase, phosphate buffer, and pH) on the measured catalytic concentration of adenosine deaminase (EC 3.5.4.4) was studied by Response Surface Methodology (RSM). This multivariate methodology offers an empirical approach to the study of enzyme assays and allows to detect the interaction between different variables of the system. Response-surface data showed maximum adenosine deaminase catalytic concentration at pH 7.2, adenosine 20 mmol/l, phosphate buffer 200 mmol/l and glutamate dehydrogenase 850 mu kat/l when pleural fluids were used as samples. Optimum conditions for a material containing purified adenosine deaminase from human erythrocytes differed only slightly from that obtained for the pleural fluid.