Culture and Sensitivity - Adenosine Deaminase ( ADA ) Test

Adenosine Deaminase is a vital enzyme in the metabolism of the purine nucleosides. For the adequate interpretation of adenosine deaminase (ADA), it is of utmost importance to know that the adenosine deaminase is represented by two isoenzymes namely, ADA1 and ADA2. ADA1 isoenzymes are present in every cell but its activity is highest in lymphocytes. ADA2 isoenzyme, on the other hand, is present only in the antigen presenting cells. The most common form of the extrapulmonary TB is pleural effusion or tuberculous pleurisy. Tuberculous pleurisy or pleural effusion usually contains a lower number of mycobacteria, the microscopy sensitivity and pleural fluid culture sensitivity of it is relatively low. The level of ADA is one of the diagnostic measure used to detect the possibility of TB in the patient. The level of ADA increases at the area where infection of mycobacterium is present in order to activate the lymphocytes, i.e., White Blood Cells to respond to the stimulus. In order to detect the pleural effusion the amount of ADA in the pleural fluid is tested.

With the method called as thoracentesis, a small amount of pleural fluid is collected by the health care professional using syringe and needle. The fluid is then send to the lab for the test to be carried out. The fluid can also be collected by biopsy using Abraham’s punch biopsy needle

In order to rule out the pleural effusion and diagnose pleural TB in case restricted resources, ADA measurement can be an alternative method. It is an easy, cheap yet highly sensitive and specific test for the detection of pleural TB In case of the pleural effusion or pleural TB, the level of the ADA in pleural fluid is increased Mean value of serum Adenosine deaminase level in PTB is 26 IU/L, in pneumonia patient it is, 19.48 IU/L and in that of patient of lung cancer is 15.8 IU/L

ANOVA analysis was used for the comparison of the quantitative variables and sensitivity analysis. In order to check the sensitivity and specificity of the serum ADA in the Pleural TB diagnosis, Crow Rock chart was used The cut off value of the ADA test was measure by the Receiver Operating Characteristic curve (ROC curve). If the value of the test is below 4 it is considered normal but a value more than 4 is considered abnormal.