OBJECTIVES/GOALS: Venous thromboembolism (VTE) is a major cause of morbidity and mortality. Due to its relatively low incidence, prospective studies are limited. This makes administrative claims a promising data source to study VTE. We sought to examine the reproducibility of results using different VTE definitions from the published literature. METHODS/STUDY POPULATION: We conducted a retrospective analysis of a random 10% sample of the 2010-2022 IQVIA LifeLink PharMetrics Plus™ database, an administrative claims database representative of the commercially insured population of the United States. We selected cancer patients undergoing major gastrointestinal surgery, who have a higher risk for postoperative VTE (deep venous thrombosis [DVT] and/or pulmonary embolism [PE]). VTE was defined using ICD-9-CM and ICD-10-CM codes using definitions from 4 individual published studies. We compared the 4 definitions with respect to the incidence of VTE and factors associated with post-discharge VTE using standard univariate and multivariable logistic regression models. The same logistic regression models were used for each of the 4 definitions. RESULTS/ANTICIPATED RESULTS: There were substantial differences in VTE coding among the 4 definitions (range 107 to 225 ICD-9/10 codes for DVT and 12 to 24 codes for PE). The eligible population comprised 2,360 patients (49% female) with a median age of 49 years (interquartile range 47-52 years). During the index surgery hospitalization, a total of 58, 62, 63, and 83 patients developed VTE using the 4 definitions. In the 2,126 patients eligible for VTE prophylaxis, a total of 108, 68, 73, and 107 patients developed post-discharge VTE (range for DVT 35 to 81, range for PE 39 to 76). On multivariable analysis, factors independently associated with VTE included age using 1 of 4 definitions, esophageal surgery type using 3 of 4 definitions, and liver surgery type and Elixhauser score using all 4 definitions. DISCUSSION/SIGNIFICANCE: The incidence of VTE is directly affected by differences in ICD-9/10 codes used. Definitions for important clinical outcomes should be standardized when using administrative claims data in order to improve reproducibility of findings.