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Risk factors among outpatients and hospitalized patients with VTE using population-based surveillance data from two US counties 2012–2014
Karon Abe1, Alys Adamski1, Aaron Wendleboe2, Nimia Reyes1, Gary Raskob2, Thomas Ortel3
1Division of Blood Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA, United States/2Hudson College of Public Health, University of Oklahoma Health Sciences , Norman, OK, United States/3Division of Hematology, Duke University Medical Center, , Durham, NC, United States

Background:  Studies suggest up to 50% of VTEs are hospital-associated; though, the majority of VTEs occur outside the hospital setting.  The availability of US population-based VTE surveillance in two counties allows for the evaluation of risk factors among outpatients with VTE compared to patients with a VTE present on admission or that develop a VTE during hospitalization. A better understanding of these factors may have clinical implications, especially considering the expanded treatment options for VTE and shortened hospital stays. Objective:  To characterize the prevalence of risk factors among outpatients with VTE compared to patients with a VTE present on admission or that develop a VTE during hospitalization. Methods:  US population-based VTE surveillance datasets from Oklahoma and Durham counties (April 2012–March 2014) were combined in a collaboration with the Centers for Disease Control and Prevention, the University of Oklahoma Health Science Center, and Duke University.  From this analysis, we selected VTE events among patients >18 years of age. We defined 3 event groups: inpatient VTE, diagnosed after ≥2 days after hospital admission, outpatient VTE resulting in hospitalization, diagnosed <2 days after hospital admission, and outpatient VTE treated at home.  Chronic disease included congestive heart failure, hemoglobinopathies, and stroke or myocardial infarction in the past 3 months. Data were assessed by admission status using chi-square analysis and Fischer’s exact test, as appropriate. Results: This study included 4,268 confirmed VTE events.  Approximately 75% (n=3,218) of the VTEs developed outside the hospital [30.2% (n=1,290) treated at home; 45.2% (n=1,928) admitted to hospital] and 24.6% (n=1,050) during the hospital stay. Recent hospitalization of 2 or more days and prior hospitalizations and/or surgery within 90 days, accounted for 31.1% of all VTEs.  Outpatients with VTE treated at home were more likely to be less than 60 years of age and without active cancer compared to either of the hospitalized groups.  Both outpatient groups of patients with VTE were more likely to be overweight/obese, have a history of previous VTE, and have VTE symptoms compared to patients with VTE diagnosed during hospitalization. Additionally, outpatients with VTE, whether admitted to the hospital or not, were less likely than patients with VTE diagnosed during hospitalization to have health insurance or to be receiving VTE prophylaxis treatment.  Outpatients with VTE who were hospitalized were more likely to have a pulmonary embolism than either outpatients treated at home or patients with VTE diagnosed during hospitalization.  Chronic disease and death were greatest among patients with VTE diagnosed during hospitalization.  These two factors as well as race, provoking status and current anticoagulant treatment were statistically different among all three groups. Conclusions: VTEs that occurred after 2 or more days in the hospital were associated with chronic conditions and death. Nonetheless, outpatients with VTE, whether hospitalized or not, showed several compounding risk factors for VTE and lower frequencies of prophylaxis and current anticoagulant treatment. Continued vigilance in the clinical management of VTE in the outpatient setting presents a broader opportunity to reduce and/or prevent further morbidity and mortality due to VTE.