Despite decades of attention, well-publicized guidelines, and ongoing quality improvement efforts, rates of VTE prophylaxis among general medical patients remain stubbornly low. In this cross-sectional study of patients from 376 US hospitals, representing approximately 10% of all patients hospitalized in the US, we found that less than 40% of patients who appeared to be candidates for VTE prophylaxis according to the ACCP guidelines actually received any. As has been observed with other treatments, we found that prophylaxis rates vary varied widely, not only across hospitals, but also among attending physicians within hospitals, and that physician and hospital practice outweighed the patients’ own risk of VTE in determining whether or not a patient would receive prophylaxis.
The rates of prophylaxis observed in the hospitals included in our study were lower than those reported in other contemporary studies. For example, both the prospective ENDORSE study8
and the IMPROVE registry7
found that prophylaxis rates among US medical patients meeting ACCP criteria exceeded 60%. There may be several explanations for this discrepancy. First, we measured only prophylaxis begun by hospital day 2, whereas the other studies included prophylaxis at any time. Using that measure, however, only increased our rates slightly, to 45%. Second, we had no direct information on either patient mobility or whether patients had been admitted for comfort care only. Some of the patients in our sample may not have been candidates if they were mobile or comfort measures only. It is likely that excluding both types of patients would have improved our overall rates. Finally, these other studies included limited numbers of US patients and hospitals. Reports of prophylaxis rates at individual institutions, especially after quality improvement initiatives, may be substantially higher. We also found that in 3% of our study hospitals, more than 70% of patients received prophylaxis, but we also found a number of hospitals where prophylaxis was seldom used. Small, rural, non-teaching hospitals tended to have the lowest rates of prophylaxis, and these may not have been included in other studies. The rate we observed in large teaching hospitals is closer to what others have observed.
Because pharmacological prophylaxis involves painful injections between one and three times daily, carries a risk of thrombocytopenia and bleeding, and can be expensive, it should be reserved for patients at moderate to high risk for VTE. The estimation of risk, however, is not straightforward, and the Joint Commission does not endorse a specific risk prediction tool.9
While prior studies have focused on prophylaxis rates among patients meeting ACCP criteria for prophylaxis, they did not evaluate the effects of additional risk factors and were thus unable to assess how prescribing patterns were influenced by the overall risk of VTE. Although our sample consisted entirely of patients considered to be in need of prophylaxis according to current guidelines, we found that physicians appear to prescribe prophylaxis more selectively, taking into account individual risk factors. As evidence of this risk-based decision making, we noted that patients at highest risk were 50% more likely to get prophylaxis than those at low risk.
Finally, we found that which form of chemoprophylaxis a patient receives is largely determined by the preferences of the physicians and hospitals where they received care. In contrast to ENDORSE and IMPROVE, we found that low molecular weight heparin was prescribed more often than unfractionated heparin. For patients receiving recommended prophylaxis, just over 1/3 of hospitals used one method of chemoprophylaxis almost exclusively, perhaps reflecting formulary decisions or prescribing guidelines, and 49% of physicians prescribed just one form of chemoprophylaxis, with more choosing unfractionated heparin. This pattern is not surprising, given that neither form of heparin has been definitively shown to be more effective, safer, or overall less expensive.
Our study has a number of limitations. First, it is a retrospective study based on hospital claims data. Nevertheless, the highly detailed nature of our dataset allowed us to identify risk factors (e.g., urinary catheter) and treatments that cannot be obtained from commonly used sources of data. Second, we used an inclusive definition of prophylaxis, giving credit for even limited use of heparin or pneumatic compression. While a far smaller percentage of patients in our study received standard prophylaxis, this may reflect a combination of inaccurate billing and physician error. Third, venous thromboembolism is an area that has received substantial attention from quality improvement organizations and professional societies, and rates today may be higher than those seen even a few years ago.
Despite decades of advocacy for greater use of VTE prophylaxis, VTE remains a common complication of hospitalization, and medical patients continue to comprise the majority of patients with hospital-acquired VTE. The new Joint Commission reporting measures may help to redress this problem. Our results suggest that most institutions still have a long way to go to achieve the Joint Commission goals. Our findings also have important implications for the implementation of Joint Commission reporting. Our study confirmed that almost all doctors prescribe VTE prophylaxis12
and that they are more likely to prescribe it for higher risk patients than lower risk ones. Still, the differences in rates between hospitals are much greater than the differences among patient risk groups within hospitals. The true determinant of hospital rates remains unknown, but they may reflect either local beliefs about the value of prophylaxis or quality improvement initiatives (e.g., checklists or other reminder systems). Although higher rates may be achievable by encouraging physicians to prescribe VTE prophylaxis for almost all medical patients,13
it is not clear that such an unbalanced strategy will result in better patient care. Our results suggest that within hospitals, patient risk had only a modest influence on physician decision making. Consequently, as prophylaxis rates rise for moderate and high-risk patients (appropriate prescribing), they also increase for low-risk patients (overprescribing). The Joint Commission measures, however, require justification only for failure to prescribe; they do not recognize or discourage overprescribing. Given that symptomatic VTE may occur in less than 1% of medical inpatients14
and that VTE prophylaxis has not been shown to decrease mortality,3
concerns about bleeding risks and the costs associated with prescribing for low-risk patients should be taken seriously.15,16
Further improvements in VTE prophylaxis for medical patients might best be served by the development of better risk stratification tools and reporting metrics that balance underprescribing with overprescribing.