Background: Increasingly, clinical practice guidelines are recommending venous thromboembolism (VTE) risk stratification for hospitalized medical patients and targeted use of pharmacologic prophylaxis in high-risk patients. Implied in this approach is avoidance of pharmacologic prophylaxis in low-risk patients, but the safety of eliminating pharmacologic prophylaxis in this cohort has not been well studied.
Methods: The Michigan Hospital Medicine Safety Consortium (HMS), a multi-hospital quality collaborative, reviewed VTE rates and the influence of pharmacologic prophylaxis among medical patients classified as low-risk based on commonly used risk models. Using web-based data entry, trained abstractors at 48 Michigan hospitals collected detailed demographic and clinical data, including risk factors for VTE, use of pharmacologic prophylaxis, and VTE events through 90 days after discharge for adult medical patients with a length of stay > 1 day. Obstetric or surgical patients, patients admitted directly to the intensive care unit, and patients receiving systemic anticoagulation were excluded from this analysis. VTE outcomes, including proximal upper and lower extremity deep vein thrombosis and pulmonary embolism, were determined by medical record review and phone follow-up. Caprini scores of 0 – 2, 0 – 4, and Padua scores < 4 were used to define low-risk. Chi-square tests and logistic regression with case-mix adjustment via the Charlson comorbidity index were used to assess differences in VTE among low-risk patients by receipt of pharmacologic prophylaxis.
Results: Risk classifications were assessed using data collected on a total of 67,834 patients. Based on the various low-risk definitions, the overall rates of VTE including rates by receipt of pharmacologic prophylaxis are shown in the table. Overall rates of VTE in-hospital and at 90 days post-discharge were low and did not differ by receipt of pharmacologic prophylaxis for any of the low-risk definitions. Further, multivariable logistic regression results indicate the odds of VTE were not reduced for patients receiving pharmacologic prophylaxis in any of low-risk categories (odds ratio (OR) for prophylaxis among Caprini 0 – 2 = 0.87 [0.49 – 1.52], p = 0.62; OR for prophylaxis among Caprini 0 – 4 = 0.83 [0.60 – 1.15], p = 0.26; OR for prophylaxis among Padua < 4 = 0.96 [0.75 – 1.22], p = 0.72).