Expression of tissue factor mRNA in thrombosis associated with antiphospholipid syndrome.

Tissue factor (TF) is a procoagulant protein associated with increased risk of thrombotic events in antiphospholipid syndrome (t-APS). The mechanisms by which TF levels are increased in APS have not yet been established. The aim of this study was to investigate whether TF mRNA expression is associated with TF levels and thrombosis in APS. We compared levels of circulating TF and high sensitivity C-reactive protein (hs-CRP) between t-APS and controls (individuals without thrombosis). The association between TF mRNA expression, quantified by real time quantitative polymerase chain reaction, and t-APS was accessed using regression analysis. We included 41 controls and 42 t-APS patients, mean age was 41 years old (SD 14) in both groups. Hs-CRP and TF levels were higher in t-APS patients (mean hs-CRP levels 0.81 mg/dL [SD 1.88] and median TF levels 249.0 pg/mL [IQR 138.77-447.61]) as compared to controls (mean hs-CRP levels 0.24 mg/dL [SD 0.26] and median TF levels 113.0 pg/mL [IQR 81.17-161.53]; P = 0.02 and P < 0.0001, respectively). There was no correlation between TF mRNA expression and TF levels in t-APS (r - 0.209, P = 0.19). TF mRNA expression was not associated with t-APS (adjusted OR 1.16; 95%CI 0.72-1.87). Despite circulating TF levels being higher in patients with t-APS than in controls, TF mRNA expression was similar between groups. The results demonstrate that TF mRNA expression is not associated with levels of circulating TF and hypercoagulability in t-APS.

Circulating levels of tissue factor and the risk of thrombosis associated with antiphospholipid syndrome.

The mechanisms behind the severe hypercoagulable state in antiphospholipid syndrome (APS) have not yet been fully elucidated. Knowledge on the etiology of thrombosis in APS is needed to improve treatment. We performed a case control study to evaluate the association of the levels of circulating tissue factor (TF) with thrombotic APS and unprovoked venous thromboembolism (VTE), as compared with controls without a history of thrombosis. Study participants were selected in the same geographic area. Linear regression was used to evaluate possible determinants of TF levels among controls and logistic regression was used to evaluate the association between TF, unprovoked VTE and t-APS. TF levels were grouped into three categories based on: below 50th percentile [reference], between 50-75th percentiles [second category] and 75th percentile [third category]. Two hundred and eighty participants were included in the study; 51 patients with unprovoked VTE, 111 patients with t-APS and 118 control individuals. The levels of TF were not associated with an increased risk of unprovoked VTE, as compared with controls. The adjusted odds ratio for t-APS was 2.62 (95%CI 1.03 to 6.62) with TF levels between 50-75th percentiles and 8.62 (95%CI 3.76 to 19.80) with TF levels above the 75th percentile, as compared with the reference category (below the 50th percentile). In the subgroup analysis, higher levels of TF were associated with both arterial and venous thrombosis in APS and with both primary and secondary APS. Circulating TF is associated with thrombotic complications related to APS, but not with the risk of unprovoked VTE.