Platelet Aggregation Test
Platelet aggregation testing is a specialized laboratory investigation that evaluates platelet function and is crucial in diagnosing inherited and acquired platelet disorders in pediatric patients.
Key Points
- Gold standard for platelet function assessment
- Essential for diagnosing platelet disorders
- Multiple agonists evaluate different activation pathways
- Light transmission aggregometry is the reference method
Scientific Basis
Principles of Testing:
- Measures platelet response to various agonists
- Evaluates multiple activation pathways
- Quantifies aggregation percentage
- Assesses response patterns
Methodology
Sample Requirements:
- Fresh whole blood (less than 4 hours old)
- Specific collection tubes required
- Temperature-controlled processing
- Platelet-rich plasma preparation
- Careful handling to avoid activation
Common Agonists Used:
- Adenosine Diphosphate (ADP):
- Concentrations: 2μM and 10μM
- Tests P2Y12 receptor function
- Essential for primary wave evaluation
- Collagen:
- Concentrations: 1-2μg/mL
- Tests GPVI pathway
- Evaluates shape change response
- Epinephrine:
- Concentration: 5-10μM
- Alpha-2 adrenergic response
- Secondary aggregation assessment
- Ristocetin:
- Concentrations: 0.5-1.5mg/mL
- vWF-dependent aggregation
- Critical for vWD diagnosis
Clinical Applications
Primary Indications:
- Unexplained bleeding tendency
- Family history of platelet disorders
- Pre-operative assessment
- Monitoring antiplatelet therapy
- Investigation of thrombocytopathy
Specific Pediatric Disorders:
- Inherited Conditions:
- Glanzmann thrombasthenia
- Bernard-Soulier syndrome
- Storage pool defects
- Signal transduction defects
- Acquired Disorders:
- Medication effects
- Uremia
- Liver disease
- Post-cardiac surgery
Result Interpretation
Normal Response Patterns:
- Primary wave characteristics
- Secondary aggregation features
- Shape change assessment
- Lag phase evaluation
- Maximum aggregation percentage
Abnormal Patterns:
- Decreased Response:
- Receptor defects
- Signaling pathway abnormalities
- Storage pool deficiency
- Medication effects
- Absent Response:
- Severe receptor defects
- Complete pathway blocks
- Technical issues
Pediatric-Specific Considerations
- Age-specific reference ranges
- Sample volume limitations
- Developmental differences
- Technical modifications needed
- Interpretation challenges
Pre-analytical Variables
- Medication history critical
- Dietary restrictions
- Time of collection
- Transport conditions
- Processing delays
Quality Assurance
- Daily controls required
- Temperature monitoring
- Reagent validation
- Equipment calibration
- Staff competency assessment
Modern Developments
New Technologies:
- Whole blood aggregometry
- Impedance aggregometry
- Flow cytometry integration
- Point-of-care testing
- Microfluidic devices
Limitations
- Time-sensitive processing
- Technical expertise required
- Large sample volume needed
- Cost considerations
- Standardization challenges
Troubleshooting Guide
- Poor sample quality management
- Temperature control issues
- Reagent problems
- Equipment malfunctions
- Result interpretation challenges
