For a long time we’ve felt that performance measures for VTE prophylaxis may be resulting in many low-risk patients receiving unnecessary prophylaxis. Now another study has questioned whether we are overusing prophylaxis in general medical patients. Flanders et al reported the results of a large multihospital performance improvement collaborative in Michigan (Flanders 2014). They looked at VTE events occurring within 90 days of hospital admission and stratified the results by hospital performance on a VTE prophylaxis measure. Overall, the rate of VTE events in this medical population was very low. When stratified into tertiles (prophylaxis rates 85.8%, 72.6% and 55.5% for high, moderate and low hospitals respectively) they found no difference in the VTE rates. Their results suggest that efforts to increase the rates of VTE prophylaxis in non-critically ill general medical patients may not substantially reduce the rate of VTE.
The accompanying commentary (Rothberg 2014) is also very thoughtful. One interpretation is that giving prophylaxis to large numbers of low-risk medical patients does not significantly reduce VTE and exposes patients unnecessarily to painful injections, creates excess costs and might increase the risk of bleeding. Rothberg notes that the fundamental problem is lack of validated tools for risk assessment in this population. The Caprini model has been validated in surgical, but not medical, patients. Rothberg suggests that the Padua Prediction Score (recommended in the most recent ACCP guidelines for VTE prophylaxis) might prove to be a better tool in medical patients but still needs to be validated in a medical population in the US because of differences between patients in the Italy and the US.
Our April 2014 What’s New in the Patient Safety World column “Another Rap on the VTE Prophylaxis Measure” discussed another study that questioned the utility of the VTE prophylaxis measure (JohnBull 2014). Those authors used publicly reported data from CMS to see if there was a correlation between VTE prophylaxis rates and outcome rates and found no correlation. They found that VTE rates at hospitals reporting 100% compliance with VTE prophylaxis were no different than those at hospitals in the bottom quintile of prophylaxis rates.
In our February 15, 2011 Patient Safety Tip of the Week “Controversies in VTE Prophylaxis” we highlighted a study by some very respected investigators in the surgical quality improvement field (Qadan 2011) that questioned the current recommendations on venous thrombembolism (VTE) prophylaxis in elective major surgery. The authors collected data on DVT and PE in patients electively undergoing 4 major surgical procedures (colorectal resection, total knee replacement, total hip replacement, and hysterectomy) from a large database from a consortium of academic medical centers for two periods of time (2003-2004 vs. 2007-2008). The study demonstrated a substantial increase in the use of pharmacologic DVT prophylaxis between the two time periods. Yet the rates of DVT and PE were not significantly impacted by this increased use of such prophylaxis. Moreover, the overall rates of DVT and PE were actually quite low and the rates in patients who did not receive pharmacoprophylaxis actually decreased between the two time periods. The authors concluded that this may show that clinical judgment of physicians in choosing which patients need pharmacoprophylaxis is remarkable.
In our November 2013 What’s New in the Patient Safety World column “Are VTE Measures Flawed as Quality Measures?” we highlighted a study () that looked at almost a million surgical patients in almost 3000 hospitals for VTE prophylaxis rates, VTE event rates, and use of imaging in VTE screening. They found that greater hospital VTE prophylaxis adherence rates were weakly associated with worse risk-adjusted VTE event rates. When they looked at hospitals with higher “structural” quality scores (based on 8 factors commonly thought to be associated with higher commitment to quality) they found higher VTE prophylaxis adherence rates but worse risk-adjusted VTE rates. Risk-adjusted VTE rates increased significantly with VTE imaging use rates in a stepwise fashion, leading to their conclusion that surveillance bias limits the usefulness of the VTE quality measure for hospitals.
The time has come to refine the VTE prophylaxis performance measures to ensure that we are not creating unintended consequences. It would not be the first time performance measures have created such. We all recall the original CMS measure for prompt antibiotic administration in patients with community acquired pneumonia resulted in many patients not having pneumonia at all receiving unnecessary antibiotics.
But critical to refining the VTE prophylaxis measure, if it is to be kept at all, will be to standardize on a validated risk assessment tool and remove the surveillance bias that may affect rates.
Some of our prior columns on issues related to VTE prophylaxis measures:
February 15, 2011 “Controversies in VTE Prophylaxis”
November 2013 “Are VTE Measures Flawed as Quality Measures?”
April 2014 “Another Rap on the VTE Prophylaxis Measure”
Flanders SA, Greene T, Grant P, et al. Hospital Performance for Pharmacologic Venous Thromboembolism Prophylaxis and Rate of Venous Thromboembolism. A Cohort Study. JAMA Intern Med. 2014; 174(10): 1577-1584
Rothberg MB. Venous Thromboembolism Prophylaxis for Medical PatientsWho Needs It? JAMA Intern Med 2014; 174(10): 1585-1586
Qadan M, Polk HC, Hohmann SF, Fry DE. A reassessment of needs and practice patterns in pharmacologic prophylaxis of venous thromboembolism following elective major surgery. Ann Surg 2011; 253(2): 215-220
JohnBull EA, Lau BD, Schneider EB, et al. No Association Between Hospital-Reported Perioperative Venous Thromboembolism Prophylaxis and Outcome Rates in Publicly Reported Data (Research Letter). JAMA Surgery 2014; online first February 5, 2014
Bilimoria KY, Chung J, Ju MH, et al. Evaluation of Surveillance Bias and the Validity of the Venous Thromboembolism Quality Measure. JAMA 2013; 310(14): 1482-1489
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