A few previous studies have examined

A few previous studies have examined Factor Xa inhibitors for VTE prophylaxis in hip fracture patients. In a 2001 paper, Eriksson et al. studied 1250 patients with hip fractures that had been randomized to either postoperative Factor Xa inhibitor or enoxaparin [13]. Each patient received bilateral venography post-operatively to assess for DVT, which ensured that even asymptomatic VTE were detected. The authors found that at post-operative day 11, the rates of DVT were 7.9% in the XaI group and 18.8% in the enoxaparin group, which were significantly different in their statistical analysis [13]. The group also found there were significantly more “minor bleeding” complications in the XaI cohort [13]. More recently, Sasaki et al. randomized a smaller group of 84 hip fracture patients to XaI or enoxaparin following surgical treatment of hip fractures [6]. These authors found a similar trend compared to Eriksson et al [13]: lower rates of VTE in the XaI group compared to the enoxaparin group, with a trade-off of more complications related to bleeding6. In the current study, we were able to include a greater number of patients than either of the previously mentioned studies by drawing on a large national claims database. However, our work was retrospective in nature compared to the prospective Eriksson and Sasaki studies, and this did introduce some significant differences into the baseline characteristics for our cohorts that are absent in the aforementioned randomized controlled trials. One important methodologic difference is that in this study, outcomes were based on CPT and ICD-9 codes, so VTE events were only detected if they pepstatin were clinically significant. This may partially account for the differences in VTE rates between our study and Eriksson’s, in which routine venography was performed to detect even asymptomatic DVTs [13]. Additionally, at 2 weeks from surgery (which most corresponds to the time point studied by Eriksson) we found no significant difference between DVT rates for our three cohorts (although we did find a difference at thirty days), and while there was a significant difference in PE rates at all time points, enoxaparin had lower rates than either XaI or warfarin. Finally, in this study there were no significant differences in bleeding complications. This study has multiple limitations, including those inherent to large database studies based on administrative claims: First, the accuracy of the data collected is dependent on the accuracy of the initial coding; subsequent analysis of this data assumes that the coding is accurate and complete. This also means that Imprinting is unknown how VTE events were diagnosed in this study (ultrasound versus venography); the only information available if whether a relevant code was entered. Additionally, unlike a traditional retrospective chart review, individualized patient data is unavailable in the database, and specific variables or outcomes cannot be tied to a particular patient. This means that certain analyses, such as regression or propensity score matching, cannot be performed. Beyond the inherent limitations of database studies, this particular study is limited by the lack of an antiplatelet (aspirin) cohort. A cohort of patients that had received aspirin for VTE prophylaxis would have been ideal to include, since this agent is commonly used for this purpose and was previously studied with high quality methodology [3]. Unfortunately, the number of patients in such a cohort obtained via the claims database used would have been too small to allow for a meaningful comparison. This is likely partially related to the fact that medications tracked by the database must be filled via prescription, and many patients that used aspirin for VTE prophylaxis may have been instructed to obtain their aspirin over-the-counter. Additionally we excluded patients who had been on aspirin pre-operatively, and this may have eliminated a large number of patients who were instructed to continue their home regimen for prophylaxis following surgery. Finally, we chose to exclude patients who were treated for hip fracture with total hip arthroplasty (THA) from the study. This was decided for two reasons: 1) multiple studies already exist regarding the use of XaI in THA, and 2) THA is perhaps a more “extensive” procedure than others commonly performed for hip fracture, and including these patients could result in a significant number of outliers in terms of outcome measures like anemia, bleeding, and transfusion. Despite these limitations, this study is one of the largest to date to assess the efficacy of Factor Xa inhibitors for VTE prophylaxis in hip fracture patients and directly compare these agents to others commonly used for chemoprophylaxis.