Summary
Growing evidence indicates that rheumatoid arthritis (RA) is associated with an increased
risk for thromboembolic cardiovascular events. We investigated thrombin generation
profiles in RA patients and their dependence on plasma factor/inhibitor composition.
Plasma factor (F) compositions (II, V, VII, VIII, IX, X), antithrombin and free tissue
factor pathway inhibitor (TFPI) from 46 consecutive RA patients with no cardiovascular
events (39 female, 7 male, aged 57 [range, 23–75] years; DAS28 [Disease Activity Score]
5.2 ± 1.1) were compared with those obtained in age- and sex-matched apparently healthy
controls. Using each individual’s plasma coagulation protein composition, tissue factor-
initiated thrombin generation was assessed both computationally and empirically. RA
patients had higher fibrinogen (4.18 [IQR 1.09] vs. 2.56 [0.41] g/l, p<0.0001), FVIII
(226 ± 40 vs. 113 ± 15%, p<0.001), PC (107 [16] vs. 100 [14]%, p<0.001), and free
TFPI levels (22.3 [2.2] vs. 14.7 [2.1] ng/ml, p<0.001). DAS28, but not age, RA duration,
or C-reac- tive protein, was associated with FV, FVIII, FIX, FX, antithrombin, and
free TFPI (r from 0.27 to 0.48, p<0.05). Intergroup comparison of computational thrombin
generation profiles showed that in RA patients, maximum thrombin levels (p=0.01) and
the rate of thrombin formation (p<0.0001) were higher, whereas the initiation phase
of thrombin generation (p<0.0001) and the time to maximum thrombin levels (p<0.0001)
were longer. Empirical reconstructions of the populations reproduced the thrombin
generation profiles generated by the computational model. Simulations of thrombin
formation suggest that blood plasma composition, i.e. a marked increase in FVIII,
somewhat counterbalanced by free TFPI, contributes to the prothrombotic phenotype
in RA patients.
Keywords
Inflammation - plasma composition - prothrombotic phenotype - rheumatoid arthritis
- thrombin generation