Determination of Plasma Tissue Factor Antigen and Tissue Factor-Bearing Microparticles Activity in Healthy Subjects

Abstract

Background: Tissue factor (TF) is an integral membrane protein, normally separated from the blood by the vascular endothelium, which plays a key role in the initiation of blood coagulation. TF is present in plasma in various forms, including microparticles (MPs) and alternatively spliced TF. MPs are small (< 1 μm) membrane vesicles generated by activated or apoptotic cells. Levels of TF antigen (TF-Ag) and tissue factor-bearing microparticles (MP-TF) activity from different origins are thought to be associated with hypercoagulable states. The aim of the present study was to determine the reference range for plasma levels of TF-Ag and MP-TF activity in healthy subjects. Methods:To establish the reference range for plasma levels of TF-Ag and MP-TF activity and study the impact of sex and age we recruited 120 healthy subjects of Bulgarian nationality aged between 18 and 65. The selection criteria for the reference group were made to comply with the generally approved recommendations of the International Federation of Clinical Chemistry (IFCC). Clinical and routine hematological, biochemical and coagulation tests were performed to assess their health status. Plasma levels of TF-Ag were determined using ELISA and MP-TF activity by means of bio-immunoassay. Results:The reference range given as 95% of the measured values was defined for TF-Ag plasma levels with 59.2 pg/ml (90% CI: 50.9 -68.2) to 250.9 pg/ml (90% CI: 234.6-267.0) and for plasma levels of MP-TF activity with 0.03 pg/ml (90% CI: 0.01-0.06) to 0.47 pg/ml (90% CI: 0.43-0.50). We found no sex-related differences in plasma TF-Ag and MP-TF activity (p > 0.05), which obviates the need for separate reference intervals for men and women. Single-factor dispersion analysis found no age dependency of plasma levels for TF-Ag and MP-TF activity (p > 0.05) in the age range 18-65. Conclusion:The reference values for TF-Ag and MP-TF activity plasma levels calculated according to the type of distribution of results can be used as baseline criteria in clinical laboratory studies and for clinical purposes.of thrombin and the subsequent conversion of fibrinogen to fibrin