Hospital Associated Venous Thromboembolism in Oklahoma County

Introduction: Venous thromboembolism (VTE) is a leading cause of death and disability of the adverse outcomes associated with a hospital stay among low, middle, and high income countries evaluated by the WHO Patient Safety Program.

Objective: Compare characteristics and risk factors for hospital associated and non-hospital associated cases of VTE in Oklahoma County from April 1, 2012 to March 31, 2014.

Methods: In collaboration with the Centers for Disease Control and Prevention (CDC), a population-based surveillance system for VTE was established in Oklahoma County, OK between April 1, 2012-March 31, 2014 to estimate the incidences of first-time and recurrent VTE events. The Commissioner of Health made VTE a reportable condition and delegated surveillance-related responsibilities to the University of Oklahoma, College of Public Health. Active surveillance involved reviewing imaging studies (e.g., chest computed tomography and compression ultrasounds of the extremities) from all inpatient and outpatient facilities in the county and collecting demographic, treatment and risk factor data on all VTE case-patients. Hospital associated VTE is defined as a VTE diagnosis made either during the hospital stay or within 90 days of hospital admission, regardless of the reason for hospitalization. Odds ratios and 95% confidence intervals (CI) were calculated. Those age 80+ years were used as the referent age group. Comparisons between hospital associated and non-hospital associated VTE cases were made by using two-sided χ²tests.

Results: We identified 2,737 patients with imaging-confirmed VTE. Of these, 1,223 (44.7%) cases were identified as hospital associated and 1,514 (55.3%) cases as non-hospital associated VTE. Of the hospital associated VTE cases, 863 (70.6%) had VTE diagnosed while hospitalized and 360 (29.4%) were diagnosed VTE as outpatients after hospital discharge; of these 360 cases, 239 (66.4%) were re-admitted to the hospital and 121 (33.6%) were managed as outpatients. Of the non-hospital associated VTE cases, 776 (51.3%) were admitted to the hospital after diagnosis and 738 (48.7%) were treated as outpatients. The median length of stay for hospital-associated cases was 8 days (range 1-206 days). The distribution of PE (p = 0.17) and DVT (p = 0.07) were similar in hospital associated cases and non-hospital associated cases. The distributions of race (p = 0.34) and sex (p = 0.17) were similar for patients with and without hospital associated VTE; however, hospital associated cases of VTE tended to be older than non-hospital associated cases (p<0.01; 18-39 years OR = 1.7, 95% CI 1.2-2.2, 40-49 years OR = 1.8, 95% CI 1.3-2.4, 50-59 years OR = 1.3, 95% CI 1.0-1.7, 60-69 years OR = 1.1, 95% CI 0.84-1.4, 70-79 years OR = 1.2, 95% CI 0.91-1.5). Venous catheterization in the last 6 months (OR= 4.4, 95% CI 3.4-5.7), surgery (OR = 3.4, 95% CI 2.8-4.0) and trauma (OR = 3.0, 95% CI 2.3-3.9) in the last 12 months, and histories of: congestive heart failure (OR = 2.6, 95% CI 2.0-3.3), stroke (OR = 2.6, 95% CI 1.9-3.6), myocardial infarction (OR = 2.2, 95% CI 1.6-3.1), superficial vein thrombosis (OR = 1.8, 95% CI 1.3-2.5), and cancer (OR = 1.5, 95% CI 1.3-1.8) were risk factors for hospital associated cases of VTE. Hospital associated VTE cases had 3.5 times the odds of death (95% CI 2.4-5.0) than non-hospital associated cases.

Discussion: A significant proportion (45%) of the total VTE burden continues to be hospital associated. A substantial proportion of hospital associated cases are diagnosed after discharge and result in re-admission, with the potential for significant financial penalties under Medicare value-based payment programs. Hospital associated cases of VTE were older, had more risk factors, and were more likely to die than non-hospital associated cases.