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Testing for lupus anticoagulants--fresh or frozen?
1Central Laboratory, Haifa and Western Galilee, Clalit Health Services, Haifa, Israel. paulfr@clalit.org.il
Clinical Chemistry and Laboratory Medicine
|September 11, 2012
Summary
Frozen-thawed plasma significantly lowers lupus anticoagulant ratios, especially in samples with low platelet counts (<10,000/μL). This can lead to misclassification of results, impacting patient diagnosis and treatment.
Area of Science:
- Hematology
- Clinical Chemistry
- Coagulation Diagnostics
Background:
- Limited research exists on frozen-thawed plasma's impact on lupus anticoagulant testing.
- Accurate lupus anticoagulant testing is crucial for diagnosing thrombotic disorders.
Purpose of the Study:
- To investigate the effect of frozen-thawed plasma on lupus anticoagulant ratios.
- To determine if low platelet counts exacerbate changes in dRVVT ratios after freezing.
Main Methods:
- Compared dilute Russel's viper venom test (dRVVT) normalized ratios using fresh versus frozen-thawed plasma.
- Included patients with initially elevated dRVVT ratios and low platelet counts (2-7×10(3)/μL).
Main Results:
- A significant decrease (p<0.001) in dRVVT normalized ratios was observed in 13 of 14 samples after freezing.
- Six of 14 patients showed misclassification of their dRVVT ratios into the reference interval post-thawing.
Conclusions:
- Testing frozen-thawed plasma with platelet counts below 10,000/μL significantly reduces dRVVT ratios.
- While other lupus anticoagulant assays like SCT showed ratio decreases, they did not lead to misclassifications.