Enhanced thrombin and plasmin generation profiles in alpha-2-antiplasmin–deficient patients: Data from the Rare Bleeding disorders in the Netherlands study

Background: α2-Antiplasmin (A2AP) deficiency is a rare and often unidentified disorder characterized by increased fibrinolysis and subsequent bleeding. Global hemostasis assays may increase insight into the altered coagulation and fibrinolysis in these patients. Objectives: To explore thrombin and plasmin generation profiles in A2AP-deficient patients, corresponding A2AP activity levels and associated bleeding phenotypes. Methods: The Nijmegen hemostasis assay was used to assess thrombin and plasmin generation in 23 A2AP-deficient patients (median age, 50 years; 70% women) from the cross-sectional Rare Bleeding disorders in the Netherlands study. Analyzed parameters included thrombin peak height, thrombin potential, fibrin lysis time, plasmin peak height, plasmin velocity index, and plasmin potential. These parameters were expressed as percentages of a reference obtained from 37 healthy controls (median age, 46 years; 57% women). The Nijmegen hemostasis assay data were correlated with A2AP activity levels and International Society on Thrombosis and Hemostasis Bleeding Assessment Tool scores using Pearson correlation coefficients. Results: Patients’ A2AP activity levels ranged from 23% to 83% (reference range, 89%-122%). Plasmin generation increased, as evidenced by significantly shorter fibrin lysis times (73%; P < .001) and higher plasmin peak heights (203%; P < .001), plasmin velocity indices (302%; P < .001) and plasmin potentials (154%; P < .001) in A2AP-deficient patients than those in healthy controls. Moreover, significantly higher thrombin potentials (146%; P < .001) and thrombin peak heights (132%; P < .001) were observed. Enhanced plasmin generation parameters showed statistically significant correlations with lower A2AP activity levels and higher International Society on Thrombosis and Hemostasis Bleeding Assessment Tool scores. Conclusion: A2AP-deficient patients exhibited augmented plasmin generation profiles that correlated with A2AP activity level and bleeding phenotype. Interestingly, increased thrombin generation profiles were also found in these patients.