Abstract
Despite the growing number of pediatric antithrombotic clinical trials, standardized safety and efficacy outcome definitions for pediatric venous thromboembolism (VTE) clinical trials have not been updated since 2011. Many recent trials have adapted the recommended definitions, leading to heterogeneity in outcomes and limiting our ability to compare studies. The International Society on Thrombosis and Haemostasis Scientific and Standardization Subcommittee (SSC) on Pediatric and Neonatal Thrombosis and Hemostasis organized a Task Force to update the efficacy and safety outcome definitions for pediatric VTE clinical trials. The outcome definitions used in the recent pediatric antithrombotic trials, definitions recommended for adult studies, and regulatory guidelines were summarized and reviewed by the Task Force as the basis for this updated guidance. Major updates to the efficacy outcomes include the removal of VTE-related mortality as a part of a composite primary outcome and explicit inclusion of all deep venous anatomic sites. Safety outcomes were updated to include a new bleeding severity category: patient important bleeding, no intervention, which encompasses bleeding for which a patient seeks care but there is no change in management. Menstrual bleeding can now be included in any bleeding category when the criteria are met. We hope that these updated outcome definitions will allow the investigators to focus on clinically relevant and patient-important outcomes and provide standardization to facilitate continued high-quality evidence for the use of antithrombotic therapies in children.