Ristocetin Platelet Aggregation Testing with a Platelet Count of 145
Yes, a ristocetin platelet aggregation test performed on a patient with a platelet count of 145 × 10^9/L can be considered accurate and reliable for diagnostic purposes. 1
Platelet Count Requirements for Aggregation Testing
- The International Society on Thrombosis and Haemostasis (ISTH) indicates that thrombin generation increases linearly with platelet counts up to a plateau of 100-150 × 10^9/L 1
- A platelet count of 145 × 10^9/L is within the acceptable range for reliable platelet function testing, as it exceeds the minimum threshold of 100 × 10^9/L 1
- While this count represents mild thrombocytopenia (normal range typically 150-450 × 10^9/L), it is sufficient for accurate ristocetin-induced platelet aggregation testing
Interpretation Considerations
When interpreting ristocetin platelet aggregation results with a platelet count of 145 × 10^9/L:
- Expect slightly wider reference intervals compared to samples with normal platelet counts 2
- The coefficient of variation for ristocetin aggregation can be higher than other agonists, particularly at lower concentrations 3
- For ristocetin specifically, testing remains feasible and diagnostically valuable even at lower platelet counts 2
Quality Control Measures
To ensure accuracy of results:
- Perform tests in duplicate with a coefficient of variation applied to each result 4
- Repeat duplicate tests with >20% difference 4
- Consider including appropriate controls (known normal and abnormal samples) with each test run 4
- If results are borderline or inconclusive, repeat the test with a fresh sample 4
Clinical Applications
Ristocetin-induced platelet aggregation at this platelet count remains valuable for:
- Diagnosing von Willebrand Disease (VWD) 5, 6
- Distinguishing between VWD and other platelet function disorders 5
- Evaluating platelet hyperreactivity 7
Potential Pitfalls and Limitations
- Be aware that ristocetin testing shows higher variability than other agonists, with coefficients of variation ranging from 42% to 160% at lower concentrations (1.0 mg/mL) 3
- Aspirin ingestion can affect the second phase of ristocetin-induced platelet aggregation at low concentrations but doesn't affect the initial phase 5
- Document any medications that might affect platelet function in the patient's history
In conclusion, while a platelet count of 145 × 10^9/L represents mild thrombocytopenia, it remains above the minimum threshold required for accurate ristocetin platelet aggregation testing according to ISTH guidelines. The test results can be considered reliable for diagnostic purposes with appropriate quality control measures in place.