University of Groningen Coagulation factor VIIa : prohemostatic drug and biomarker for thrombosis

Background: While air travel is a well-established risk factor for venous thrombosis, the underlying mechanism is still incompletely understood. We previously demonstrated coagulation activation during air travel in healthy individuals, as assessed by a rise in thrombin-antithrombin complexes. It has been suggested that venous thrombosis is initiated via the extrinsic pathway of coagulation, specifically via tissue factor-bearing microparticles. Objective: To determine whether coagulation activation during air travel proceeds via the extrinsic pathway. Assays that specifically detect the activated form of factor VII were used as a marker of extrinsic activation. Methods: We measured activity and antigen levels of FVII and FVIIa in 71 individuals before, during, and after an 8 hour flight, a movie marathon, and daily life routine. Activity levels were determined using commercially available assays. Antigen levels were determined using assays recently developed in our laboratory. Results: Activity levels of FVII and FVIIa were correlated with antigen levels (FVII r = 0.373 (95% confidence interval [CI] 0.301-0.441); FVIIa r = 0.265 (95% CI 0.188-0.339). FVII activity and antigen levels did not change during or after the flight, movie marathon, or daily life routine. FVIIa activity increased after all exposures. In contrast, FVIIa antigen levels decreased during all three exposures and normalized thereafter. Activity and antigen levels of FVII and FVIIa were not different in individuals who had increased thrombin-antithrombin levels after the flight compared to those who had not. Conclusion: Using two distinct assays that specifically detect activated FVII, we did not find any evidence for extrinsic coagulation activation during air travel.