RBC Adenosine Deaminase Activity Test

Erythrocyte Adenosine Deaminase (eADA) Activity Test

Key Points

Enzyme assay measuring ADA activity in erythrocytes
Critical for diagnosing immunodeficiency disorders
Important marker for monitoring disease progression
High specificity for certain immunological conditions

Introduction

The Erythrocyte Adenosine Deaminase (eADA) activity test measures the activity of ADA enzyme in red blood cells. This enzyme plays a crucial role in purine metabolism and is essential for proper immune system function. The test is particularly valuable in diagnosing severe combined immunodeficiency (SCID) and other immunological disorders.

Testing Procedure

Sample Collection

Blood Collection:
- 5-10 mL whole blood
- EDTA or heparin tube
- Room temperature transport
- Process within 4 hours
Sample Processing:
- Centrifugation at 3000g
- Separation of erythrocytes
- Washing with saline solution
- Preparation of hemolysate

Analytical Method

Spectrophotometric Analysis:
- Measurement at 265nm
- Temperature control at 37°C
- Reaction time monitoring
- Blank sample comparison
Enzymatic Reaction:
- Adenosine substrate
- Buffer solution pH 7.4
- Inosine formation
- Ammonia release

Quality Control

Standard curve preparation
Internal quality controls
Temperature monitoring
Calibration verification
Method validation

Result Analysis

Reference Ranges

Age-Specific Values:
- Newborns: 0.8-1.2 U/g Hb
- Infants: 0.6-1.0 U/g Hb
- Children: 0.5-0.9 U/g Hb
- Adolescents: 0.4-0.8 U/g Hb
Clinical Decision Points:
- SCID: <0.1 U/g Hb
- Carrier state: 0.3-0.5 U/g Hb
- Normal range: 0.5-1.5 U/g Hb
- Elevated: >1.5 U/g Hb

Result Interpretation Factors

Influencing Factors:
- Age of patient
- Recent infections
- Medications
- Sample handling
Common Interferences:
- Hemolysis
- Storage conditions
- Processing delays
- Temperature variations

Clinical Applications

Primary Indications

Diagnostic Applications:
- SCID screening
- Immunodeficiency evaluation
- Carrier detection
- Family screening
Monitoring:
- Treatment response
- Disease progression
- Post-transplant follow-up
- Enzyme replacement therapy

Clinical Significance

Low ADA Activity:
- SCID diagnosis
- Immunodeficiency disorders
- Carrier status
- Treatment monitoring
Elevated ADA Activity:
- Inflammatory conditions
- Certain malignancies
- Infectious diseases
- Autoimmune disorders

Treatment Implications

Management Decisions:
- Stem cell transplantation timing
- Enzyme replacement needs
- Infection prophylaxis
- Immunoglobulin therapy
Follow-up Care:
- Monitoring frequency
- Treatment adjustments
- Complication prevention
- Long-term prognosis

Limitations and Considerations

Sample stability issues
Technical expertise required
Cost considerations
Limited availability
Result turnaround time