Adenosine Deaminase (ADA)(Pleural fluid)
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Diagnose tuberculous pleural effusion, especially in high TB-burden countries like India
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🧪 ADA (Adenosine Deaminase) – Pleural Fluid
Parameter | Details |
|---|---|
Fasting Required? | ❌ Not required |
Sample Type | Pleural fluid (obtained via thoracentesis) |
Main Organs Involved | Lungs, pleura, immune system (T-lymphocytes) |
Primary Purpose | Diagnose tuberculous pleural effusion (TB pleuritis) |
🔬 What is ADA?
- Adenosine Deaminase (ADA) is an enzyme crucial for T-cell proliferation and activity.
- High ADA activity in pleural fluid indicates a cell-mediated immune response, typically seen in tuberculosis.
🧠 Why Test ADA in Pleural Fluid?
ADA levels help:
- Diagnose exudative pleural effusions of tubercular origin.
- Differentiate TB pleuritis from malignancy, bacterial pneumonia, or heart failure.
- Serve as a quick, cost-effective alternative to AFB smear or culture.
📈 Interpretation of ADA Levels in Pleural Fluid
ADA Level (U/L) | Clinical Significance |
|---|---|
< 30 U/L | TB unlikely; consider other causes (e.g. cancer, CHF, pneumonia) |
30–40 U/L | Indeterminate; correlate with cytology, lymphocyte % |
> 40 U/L | Suggestive of tuberculous pleural effusion |
> 60 U/L | Highly suggestive of TB, especially in young patients |
🔹 Interpretation is most accurate when lymphocyte predominance is present in the pleural fluid.
⚠️ Important Notes & False Positives
Condition | Possible Impact on ADA |
|---|---|
Empyema or parapneumonic effusions | Can also elevate ADA (due to neutrophilic activation) |
Rheumatoid arthritis or malignancy | May cause mildly elevated ADA levels |
HIV-positive patients | ADA may be falsely low due to immune suppression |
🔗 Recommended Conjunction Tests
Test | Purpose |
|---|---|
AFB Staining & Culture | Direct evidence of Mycobacterium tuberculosis |
GeneXpert / CBNAAT (Pleural fluid) | Molecular confirmation and rifampicin resistance |
Pleural Fluid Cytology | Rule out malignancy |
Pleural Fluid Cell Count | Lymphocyte predominance supports TB diagnosis |
ESR, CRP | Support inflammatory process |
Chest X-ray / CT Thorax | Identify effusion, pleural thickening, or lymphadenopathy |
✅ Summary Table
Test Name | ADA – Pleural Fluid |
|---|---|
Main Purpose | Diagnose tuberculous pleural effusion |
Sample | Pleural fluid via thoracentesis |
ADA > 40 U/L | Strongly suggests TB pleuritis, especially with lymphocytes |
Conjunction Tests | AFB smear, GeneXpert, cytology, imaging, cell count |
Time to Result | Usually available in 24 hours |
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