Venous thromboembolism prophylaxis in the United States: still room for improvement.

Venous thromboembolism (VTE) is one of the most common, life-threatening cardiovascular conditions in the United States, causing approximately 200,000 deaths each year.1,2 Hospitalized patients are particularly vulnerable to VTE, with approximately 42.5% of all hospitalized medical patients considered to be at increased VTE risk.3 As a result, multiple guidelines, including the prominent American College of Chest Physicians Guidelines on Antithrombotic and Thrombolytic Therapy, support the administration of measures to prevent VTE in appropriate patients.4 Although pharmacologic and, to a lesser degree, mechanical forms of prophylaxis, have been shown to significantly reduce the risk of VTE5, several studies have shown that many hospitalized patients do not receive VTE prophylaxis.6–8 In this issue of the Journal of General Internal Medicine, Rothberg et al. present a large analysis of VTE prophylaxis rates among medical patients admitted to 376 acute-care facilities in the United States, finding that a striking 64% of patients with at least a moderate risk of VTE failed to receive VTE prophylaxis by the second day of their hospitalization.9 Using an administrative database of greater than 350,000 medical inpatients with primary diagnoses indicating a moderate to high-risk of VTE, this study revealed not only overall low rates of VTE prophylaxis, but also considerable variability in utilization rates across hospitals and providers. Despite some differences in patient selection and definition of VTE prophylaxis, the low administration rates are consistent with other similar multi-institutional studies.6,10,11 A unique finding of the study was that, although prophylaxis rates varied among individual physicians, physician practice seemed to cluster around institutional means. Patients with similar VTE risk profiles had widely divergent likelihoods of receiving VTE prophylaxis depending on the admitting hospital, with variability observed by hospital size, type, and region. This variation in clinical practice among hospitals suggests that strategies aimed at improving prophylaxis rates should be directed at the institutional level. There are several limitations to this observational study using administrative data. One is the lack of information on clinical decision-making with regard to VTE prophylaxis, such as contraindications to pharmacologic VTE prophylaxis or patient preference. For example, a prior study found that contraindications excluded 10% of medical patients from receiving pharmacologic VTE prophylaxis.6 It was possible that some services may not have been consistently or uniformly captured, as they were dependent on accurate billing and utilization codes. Finally, using ICD-9 coded clinical diagnoses to classify patients into varying levels of VTE risk may be subject to misclassification and cannot completely capture the unique circumstances of individual patients, such as comfort care or highly ambulatory individuals who were thought to be at low VTE risk. Nevertheless, even allowing that some patients in this analysis may not have required or desired VTE prophylaxis, the low administration rates in the study still suggest that significant numbers of patients fail to receive appropriate VTE prophylaxis. That variation in prophylaxis administration seemed to be more dependent on region and hospital practice as opposed to individual patient factors highlights the need for continued study in system-wide and institutionally-directed interventions. The direction of further research should now focus less on describing the scope of the problem and more on how to best address barriers to quality improvement and most effectively implement solutions.