Study of Adenosine deaminase activity and IgM antibody level in the diagnosis of Tuberculosis: Hospital based cross-sectional study

Background: Tuberculosis is one of the major causes of morbidity and mortality. Adenosine Deaminase (ADA) is an enzyme required for the conversion of adenosine to inosine through purine salvage pathway.The study was conducted to achieve following objectives:(1) To estimate Adenosine Deaminase (ADA) activity in pleural fluid and serum of tuberculous patients and determine its sensitivity and specificity, (2) To determine IgM antibody level in the serum of tuberculous patients and determine its sensitivity and specificity, (3) To determine pleural fluid to serum protein ratio in tuberculosis cases and controls. Methodology: Hospital based comparative cross-sectional study was conducted. Subjects were grouped as pulmonary Tuberculosis(PTB) cases and non-PTB controls. Pleural fluid and serum of patients diagnosed with tuberculosis and controls were analyzed for ADA activity. Serum of both groups was tested for anti-TB IgM antibody. Results: In our study, 100 subjects (50 PTB cases and 50 non-PTB controls) were enrolled. Pleural fluid ADA activity was significantly higher in PTB cases (85.32±24.99 IU/L) than non-PTB controls (22.42±12.93 IU/L) (p<0.001). Serum ADA activity was also higher in PTB cases(32.40±7.07 IU/L) than controls (10.78±3.55 IU/L). The ADA assay had highest sensitivity (95.12%) and specificity (94.00%) at cut off of 40 IU/L in pleural fluid. For IgM antibody assay, a sensitivity and specificity of 63.10% and 82.0% respectively was obtained. Conclusion: The serum Adenosine Deaminase (ADA) is very useful marker of tuberculosis infection whereas serological test appears to be unreliable due to its low sensitivity.