Determinants of plasma fibrin clot lysis measured using three different assays in healthy subjects

Introduction: Several methods for measuring fibrinolytic capacity in plasma have been developed yielding frequently inconsistent results. We investigated which factors determine fibrinolytic capacity in three plasma-based assays. Material and methods: In 80 apparently healthy controls (aged 43 ± 10 years, 50 women [62.5%]) we evaluated fibrinolysis using three assays: (1) by Pieters et al. (CLT2018), (2) by Lisman et al. (CLT), and (3) by Carter et al. (Lys50). Coagulation factors and fibrinolytic proteins, including histidine-rich glycoprotein (HRG) and γ′-fibrinogen, were determined. Regression models were performed to identify determinants of lysis times. Results: Positive correlations were observed between CLT2018 and both CLT (r = 0.73) and Lys50 (r = 0.61), as well as between CLT and Lys50 (r = 0.46, all p < 0.001). The main determinants of both CLT2018 and CLT were plasminogen activator inhibitor-1 (PAI-1), followed by thrombin-activatable fibrinolysis inhibitor (TAFI) and α2-antiplasmin. Histidine-rich glycoprotein was a predictor of the longest-normal CLT2018 alone (OR 1.04, 95% CI 1.02–1.06). α2-Antiplasmin and fibrinogen levels, followed by PAI-1 and TAFI determined Lys50. After adjustment for age, sex, and body mass index, C-reactive protein (CRP) was an independent predictor of the top quartiles of the three lysis times. Conclusions: We showed that apart from PAI-1, TAFI, and α2-antiplasmin, several other factors, in particular CRP, can affect the results of global fibrinolysis tests used in research. Our findings may help understand why the choice of a specific fibrinolysis assay can affect the presence and/or magnitude of intergroup differences in fibrinolytic capacity in a given disease state.