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Updated: May 31, 2026
Extracellular Vesicle Tissue Factor Activity Assay
Published on: December 29, 2023
Pre-analytical and analytical variables affecting the measurement of plasma-derived microparticle tissue factor
R D Lee1, D A Barcel, J C Williams
1Division of Hematology/Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Introduction:
Elevated levels of tissue factor positive (TF(+)) microparticles (MPs) are observed in plasma from a variety of patients with an increased risk of thrombosis. We and others have described the measurement of TF activity in MPs isolated from plasma. The aim of this study was to investigate the effects of pre-analytical and analytical variables on TF activity of MPs isolated from blood of healthy volunteers either untreated or treated ex vivo with bacterial lipopolysaccharide.
Materials And Methods:
We evaluated the following parameters: use of different centrifugation speeds to isolate the MPs; comparison of TF activity of MPs isolated from platelet poor plasma versus platelet free plasma; effect of freeze/thaw on MP TF activity; and comparison of the MP TF activity assay with the measurement of TF protein by ELISA or flow cytometry.
Results:
MPs prepared from platelet poor plasma by centrifugation at 20,000×g or 100,000×g for 15 minutes had similar levels of TF activity. However, significantly less TF activity was found in MPs isolated from platelet free plasma compared with platelet poor plasma. Interestingly, freeze/thawing of the plasma showed donor to donor variation in MP TF activity, with a moderate increase in some individuals.
Conclusion:
TF(+) MPs can be quantitatively isolated from platelet poor or platelet free plasma by centrifugation at 20,000×g for 15 minutes. Measurement of MP TF activity in plasma may be used to detect a prothrombotic state in patients with various diseases.
Insights
Tissue factor (TF) positive microparticles (MPs) are key in thrombosis risk. Optimizing isolation methods, like using platelet-poor plasma, ensures accurate TF activity measurement for detecting prothrombotic states.
Area of Science:
- Hematology
- Thrombosis Research
- Biochemistry
Background:
- Elevated tissue factor positive (TF(+)) microparticles (MPs) are linked to increased thrombosis risk.
- Previous studies established methods for measuring TF activity in plasma-derived MPs.
- This study focuses on optimizing pre-analytical and analytical variables for MP TF activity assessment.
Purpose of the Study:
- To investigate pre-analytical and analytical factors affecting TF activity measurement in MPs.
- To determine optimal conditions for isolating TF(+) MPs from blood samples.
- To compare MP TF activity assay with protein quantification methods.
Main Methods:
- Evaluated centrifugation speeds (20,000×g vs. 100,000×g) for MP isolation.
- Compared TF activity in MPs from platelet-poor versus platelet-free plasma.
- Assessed the impact of freeze/thaw cycles on MP TF activity.
- Compared MP TF activity assay with ELISA and flow cytometry for TF protein measurement.
Main Results:
- Similar TF activity in MPs isolated by 20,000×g or 100,000×g centrifugation.
- Significantly lower TF activity in MPs from platelet-free plasma compared to platelet-poor plasma.
- Freeze/thaw cycles induced variable changes in MP TF activity across donors.
Conclusions:
- Quantitative isolation of TF(+) MPs is feasible using centrifugation (20,000×g for 15 min) from platelet-poor or platelet-free plasma.
- MP TF activity measurement is a potential biomarker for identifying prothrombotic states in various diseases.
