Plasma thrombin generation in the presence of TIX-5 may contribute significantly to a prediction model for major bleeding in patients on VKA anticoagulant therapy

Introduction: Oral anticoagulant therapy comes at the cost of a significant bleeding risk. However, it is hard to predict which patients are at risk of major bleeding. Previously we found associations of Calibrated Automated Thrombinography (CAT) parameters obtained in the presence of TIX-5 (an inhibitor of the FV activation by FXa), and plasma levels of TFPIα, γ’-fibrinogen and soluble thrombomodulin with major bleeding in the BLEEDS cohort, a cohort especially powered to find new biomarkers of major bleeding during VKA therapy. Methods: To determine and compare the predictive capability for major bleeding in the BLEEDS cohort of the above biomarkers, also in a combined model with clinical risk factors, we performed Univariable Prentice-weighted Cox regression analyses and Bayesian variable selection. Results: The highest predictive value among the laboratory measures were found for thrombin generation lagtime in the presence of TIX-5 (TIX-5 lagtime per 25% increase, hazard ratio (HR) 1.11, 95%CI 1.04–1.18, p=0.001) and full-length tissue factor pathway inhibitor (TFPIα) (per 25% increase HR 1.12, 95%CI 1.03–1.21, p=0.008), which remained significant after correction for multiple testing, and independently associated with major bleeding after Bayesian variable selection. Only the addition of TIX-5 lagtime to the clinical risk factors improved prediction of major bleeding significantly (p