Risk Factors for Inpatient Acute Venous Thromboembolism (VTE) Despite Thromboprophylaxis.

Venous thromboembolism (VTE) is the most common preventable cause of morbidity and mortality in the hospital. Adequate thromboprophylaxis has reduced the rate of hospital-acquired VTE by 50–70%; however, some inpatients still develop VTE despite thromboprophylaxis. Predictors associated with thromboprophylaxis failure are undefined.

We aimed to identify risk factors for VTE despite use of inpatient thromboprophylaxis.

We used a case-control study to determine independent predictors of inpatient VTE. We matched 94 cases discharged from the BJC HealthCare system from January 1^st, 2010 to May 31^st, 2011who developed in-hospital VTE despite thromboprophylaxis (including either pharmacological or mechanical prophylaxis or both) to 272 controls without VTE. Matching was done by hospital, age, and date of discharge. Two thirds of the sample was used as derivation model, while one third was used for validation. We used multivariate conditional logistic regression on the derivation sample to develop a VTE prediction model and validated the model. We repeated conditional logistic regression on the pooled data.

Age and sex were well-matched. Mean age was 62.8 years-old in the VTE group and 63.2 years-old in the no-VTE group. Forty-three percent were female in the VTE group, while 49% were female in the no-VTE group. Using conditional logistic regression model in the pooled data, we identified five independent risk factors for in-hospital VTE: hospitalization for cranial surgery (Odds ratio [OR] 16.1, 95% confidence interval [CI] 3.2–80.4, p<0.001), hospitalization in a critical care unit (OR 3.0, 95% CI 1.5–5.9, p=0.002), admission leukocyte count > 13 × 10³/mm³(OR 2.7, 95% CI 1.4–5.1, p=0.003), presence of an indwelling central venous catheter (OR 2.5, 95% CI 1.3–4.7, p=0.007), and admission from a long-term care facility (OR 2.1, 95% CI 1.0–4.2, p=0.04).

In the hospital setting, we derived and validated five risk factors associated with the development of VTE despite thromboprophylaxis. Clinicians should be vigilant for VTE in these patients and ensure that they have aggressive VTE prophylaxis.

No relevant conflicts of interest to declare.