Adenosine Deaminase (ADA) Test
Sample Type: Serum

Purpose:
The ADA test measures the activity of adenosine deaminase, an enzyme involved in purine metabolism and immune function. It is most commonly used to aid in the diagnosis of tuberculosis (TB), especially tuberculous pleuritis.

Clinical Use:

Primarily used in evaluating pleural effusion (fluid in the pleural space)

Helps distinguish tuberculous pleuritis from other causes of pleural effusion

Occasionally used in pericardial or peritoneal fluid analysis

Mechanism:
ADA is released by activated T-lymphocytes, especially during a cell-mediated immune response, as seen in tuberculosis infections.

Interpretation:

High ADA levels in pleural fluid suggest tuberculosis as a likely cause

Normal or low ADA levels usually rule out TB (though not definitively)

Limitations:

Elevated ADA can also occur in empyema, lymphoma, or rheumatoid disease, so clinical correlation is essential.

Serum ADA levels are less commonly used but may support other findings.