Definition of pulmonary embolism-related death and classification of the cause of death in venous thromboembolism studies: Communication from the SSC of the ISTH

Pulmonary embolism (PE)-related death is often a component of the primary outcome in venous thromboembolism (VTE) clinical studies. Definitions for PE-related death vary widely, which may lead to biased risk estimates of clinical outcomes, thereby affecting both internal and external validity of study results. We here provide a standardized definition of PE-related death and propose guidance for classification and reporting of the cause of death for clinical studies in VTE. The proposal was developed in a four-step process, including a systematic review of definitions used for PE-related death in previous studies, two subsequent surveys with VTE experts, and meetings held within the Scientific and Standardization Committee (SSC) working group until consensus on the proposal was reached. The proposed classification comprises three categories: Category A: PE-related death, category B: undetermined cause of death, and category C: cause of death other than PE. Category A includes A1: autopsy-confirmed PE in the absence of another more likely cause of death; A2: objectively confirmed PE before death in the absence of another more likely cause of death; and A3: PE is not objectively confirmed, but is most likely the main cause of death. Category B includes B1: cause of death is undetermined, despite available information; and B2: insufficient clinical information available to determine the cause of death. The use of the proposed definition will hopefully improve the accuracy of study outcomes, between-study comparisons, meta-analyses, and validity of future clinical VTE studies.