Factors Associated with Venous Thromboembolism Pharmacoprophylaxis Initiation in Hospitalized Medical Patients: The Medical Inpatients Thrombosis and Hemostasis (MITH) Study.

BACKGROUND Although guidelines recommend risk assessment for hospital-acquired venous thromboembolism (HA-VTE) to inform prophylaxis decisions, studies demonstrate inappropriate utilization of pharmacoprophylaxis in hospitalized medical patients. Predictors of pharmacoprophylaxis initiation in medical inpatients remain largely unknown. OBJECTIVE To determine factors associated with HA-VTE pharmacoprophylaxis initiation in adults hospitalized on medical services. DESIGN Cohort study using electronic health record data from adult patients hospitalized on medical services at four academic medical centers between 2016 and 2019. PARTICIPANTS Among 111,550 admissions not on intermediate or full-dose anticoagulation, 48,520 (43.5%) received HA-VTE pharmacoprophylaxis on the day of or the day after admission. MAIN MEASURES Candidate predictors of HA-VTE pharmacoprophylaxis initiation, including known HA-VTE risk factors, predicted HA-VTE risk, and bleeding diagnoses present on admission. KEY RESULTS After adjustment for age, sex, race/ethnicity, and study site, the strongest clinical predictors of HA-VTE pharmacoprophylaxis initiation were malnutrition and chronic obstructive pulmonary disease. Thrombocytopenia and history of gastrointestinal bleeding were associated with decreased odds of HA-VTE pharmacoprophylaxis initiation. Patients in the highest two tertiles of predicted HA-VTE risk were less likely to receive HA-VTE pharmacoprophylaxis than patients in the lowest (1st) tertile (OR 0.84, 95% CI [0.81, 0.86] for 2nd tertile, OR 0.95, 95% CI [0.92, 0.98] for 3rd tertile). CONCLUSIONS Among patients not already receiving anticoagulants, HA-VTE pharmacoprophylaxis initiation during the first two hospital days was lower in patients with higher predicted HA-VTE risk and those with risk factors for bleeding. Reasons for not initiating pharmacoprophylaxis in those with higher predicted risk could not be assessed.