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Rapid Responses to:
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Electronic letters published:
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Author's Reply
Comparing Apples to Apples: Weight-based LMWH vs. Weight-based IV UFH
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Jodi B Segal, M.D., M.P.H. Johns Hopkins University School of Medicine, Michael B Streiff, Eric B Bass
Send rapid response to journal:
jsegal{at}jhmi.edu Jodi B Segal, et al.
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We appreciate the analyses by Dr. Umscheid of a subgroup of the studies which were included in the systematic reviews which we identified. These analyses confirm that there is little difference in outcomes (both efficacy and safety outcomes) between weight-based UFH and weight-based LMWH. We expect that practice patterns have changed since the publication of most of these trials; it is usual practice in most institutions to use a weight-based nomogram for intravenous heparin dosing. We are pleased that Dr. Umscheid’s analyses support the recommendations in the guidelines in this current era of weight-based dosing of both UFH and LMWH. Conflict of Interest:None declared |
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Craig A Umscheid, MD, MSCE Center for Evidence-based Practice, University of Pennsylvania Health System, Rajender Agarwal and Gene Gibson.
Send rapid response to journal:
craig.umscheid{at}uphs.upenn.edu Craig A Umscheid, et al.
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In regards to the
systematic review evaluating the management of venous thromboembolism (VTE) by
Segal et al.(1), we are concerned that the analyses comparing the efficacy and
safety of low molecular weight heparin (LMWH) to unfractionated heparin (UFH)
are biased against UFH. In 1993, Raschke
et al. demonstrated the superior efficacy and safety of the weight-based UFH dosing
nomogram compared to the traditional non-weight-based UFH dosing nomogram for
the treatment of VTE.(2) But of the
approximately 45 studies included in Segal's review, only 6 (13%) compared
weight-based LMWH to weight-based intravenous (IV) UFH. Comparing weight-based LMWH to non-weight-based
UFH would result in a bias against the efficacy of UFH in heavier patients and
against the safety of UFH in lighter patients.
Using the six studies
above, we compared outcomes at 90 to 100 days of using weight-based LMWH versus
weight-based IV UFH for the treatment of VTE.
Where appropriate, we used random-effects meta-analyses to combine relative
risks from individual studies, and measured heterogeneity using the Q
statistic. We found no statistical
differences in major bleeding, mortality or recurrent VTE between patients
receiving weight-based LMWH versus weight-based IV UFH, regardless of patient
population or LMWH dosing (Table). No
significant heterogeneity was demonstrated.
A limitation of our analyses is our lower sample sizes as compared to
the "Cluster C" analyses by Segal et al. (1), which included at least
5,568 patients. Ultimately, our
recommendation for the management of VTE may have been similar to Snow et al. (3),
but our support of LMWH over IV UFH would be based on concerns regarding the
lesser effectiveness or higher
indirect costs associated with the titration of IV UFH, rather than its efficacy. 1. Segal JB et al.
Management of venous thromboembolism: A systematic review for a practice
guideline. Ann Intern Med 2007 Feb 6; 146:211-22. 2. Raschke RA et al. The weight-based heparin dosing nomogram
compared with a “standard care” nomogram: a randomized controlled trial. Ann Intern Med 1993 Nov 1; 119:874-881. 3. Snow V et al. Management
of venous thromboembolism: A clinical practice guideline from the
Conflict of Interest:None declared |
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