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John W. Eikelboom, MD; Jack Hirsh, MD
Author and Funding Information

Affiliations: Dr. Eikelboom is affiliated with the Department of Medicine, McMaster University and Population Health Research Institute and Thrombosis Service, Hamilton General Hospital. Dr. Hirsh is affiliated with the Henderson Research Centre and McMaster University.

Correspondence to: John W. Eikelboom, MD, McMaster University, Hamilton General Hospital Campus, 237 Barton St East, Hamilton, ON, Canada L8L 2X2; e-mail: eikelbj@mcmaster.ca


Financial/nonfinancial disclosures: Dr. Eikelboom has received consulting fees and/or honoraria from Astra-Zeneca, BI, BMS, Corgenix, Daiichi-Sankyo, Eisai, Eli-Lilly, GSK, Haemoscope, McNeil, and Sanofi-Aventis, and has received grants and/or in-kind support from Accumetrics, AspirinWorks, Bayer, BI, BMS, Corgenix, Dade-Behring, GSK, and Sanofi-Aventis. Dr. Hirsh has reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).


© 2009 American College of Chest Physicians


Chest. 2009;136(6):1700-1701. doi:10.1378/chest.09-1970
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To the Editor:

We welcome the opportunity to respond to the concerns raised by Zuckerman and colleagues regarding our comparison between the guidelines of the American College of Chest Physicians and those of the American Association of Orthopaedic Surgeons (AAOS)1 for the prevention of venous thromboembolism in patients undergoing major orthopedic surgery.

Zuckerman and colleagues question the validity of deep vein thrombosis (DVT) as a surrogate measure of outcome for pulmonary embolism (PE). They base their opinion on the imperfect correlation between DVT and PE, and on their view that the effects of anticoagulants on the prevention of PE are not entirely explained by their effects on DVT. We accept that DVT is not a perfect surrogate for PE and that PE is the most important outcome for patients. However, we do not accept the complete rejection by the AAOS guideline panel2 of DVT as an important outcome in the setting of venous thromboembolism prophylaxis.

Having said this, it also appears that, despite statements to the contrary, the AAOS tacitly accepts DVT as a valid outcome because they recommend anticoagulant prophylaxis for most patients undergoing elective hip and knee surgery. These AAOS recommendations are made despite a lack of benefit, from their indirect comparisons, for anticoagulant therapy in preventing PE in the observational studies that they cite. Rather than questioning the validity of DVT as a surrogate for PE, the key issue is whether the quality of the evidence that is based on the results of a reduction in the incidence of asymptomatic DVT justifies a grade 1A recommendation or whether it should be downgraded to a weaker recommendation.

The second issue raised by Zuckerman and colleagues concerns the tradeoff between the benefits and harms of thromboprophylaxis. This is a valid concern, because it is not possible to compare the benefits and harms (eg, bleeding) of anticoagulant prophylaxis when the benefits are measured by a reduction in the incidence of asymptomatic DVT. There is, however, overwhelming evidence from randomized, controlled trials that pharmacologic thromboprophylaxis, compared with placebo treatment or no treatment, reduces the incidence of PE in patients undergoing major orthopedic surgery and in other high-risk groups.37 We think that all patients undergoing major orthopedic surgery should receive a method of prophylaxis that has been proven to be effective in randomized trials.

We agree with Zuckerman and colleagues that conflicting guideline recommendations are confusing, not only for patients and health-care providers but also for third-party insurers who use guidelines to develop performance measures that influence payment. Closer collaboration between the AAOS panel and the American College of Chest Physicians panel in advance of future updates may help to resolve some of the differences.

Eikelboom JW, Karthikeyan G, Fagel N, et al. American Association of Orthopedic Surgeons and American College of Chest Physicians guidelines for venous thromboembolism prevention in hip and knee arthroplasty differ: what are the implications for clinicians and patients? Chest. 2009;135:513-520. [PubMed] [CrossRef]
 
American Academy of Orthopaedic Surgeons Clinical guideline on prevention of symptomatic pulmonary embolism in patients undergoing total hip or knee arthroplasty: adopted by the American Academy of Orthopedic Surgeons Board of Directors May 2007.Accessed October 29, 2009 Available at:www.aaos.org/research/guidelines/PE_guideline.pdf.
 
Pulmonary Embolism Prevention Trial Collaborative Group Prevention of pulmonary embolism and deep vein thrombosis with low dose aspirin: Pulmonary Embolism Prevention (PEP) trial. Lancet. 2000;355:1295-1302. [PubMed]
 
Collins R, Scrimgeour A, Yusuf S, et al. Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin: overview of results of randomized trials in general, orthopedic, and urologic surgery. N Engl J Med. 1988;318:1162-1173. [PubMed]
 
Mismetti P, Laporte S, Darmon JY, et al. Meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery. Br J Surg. 2001;88:913-930. [PubMed]
 
Leizorovicz A, Haugh MC, Chapuis FR, et al. Low molecular weight heparin in prevention of perioperative thrombosis. BMJ. 1992;305:913-920. [PubMed]
 
Cohen AT, Davidson BL, Gallus AS, et al. Efficacy and safety of fondaparinux for the prevention of venous thromboembolism in older acute medical patients: randomised placebo controlled trial. BMJ. 2006;332:325-329. [PubMed]
 

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References

Eikelboom JW, Karthikeyan G, Fagel N, et al. American Association of Orthopedic Surgeons and American College of Chest Physicians guidelines for venous thromboembolism prevention in hip and knee arthroplasty differ: what are the implications for clinicians and patients? Chest. 2009;135:513-520. [PubMed] [CrossRef]
 
American Academy of Orthopaedic Surgeons Clinical guideline on prevention of symptomatic pulmonary embolism in patients undergoing total hip or knee arthroplasty: adopted by the American Academy of Orthopedic Surgeons Board of Directors May 2007.Accessed October 29, 2009 Available at:www.aaos.org/research/guidelines/PE_guideline.pdf.
 
Pulmonary Embolism Prevention Trial Collaborative Group Prevention of pulmonary embolism and deep vein thrombosis with low dose aspirin: Pulmonary Embolism Prevention (PEP) trial. Lancet. 2000;355:1295-1302. [PubMed]
 
Collins R, Scrimgeour A, Yusuf S, et al. Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin: overview of results of randomized trials in general, orthopedic, and urologic surgery. N Engl J Med. 1988;318:1162-1173. [PubMed]
 
Mismetti P, Laporte S, Darmon JY, et al. Meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery. Br J Surg. 2001;88:913-930. [PubMed]
 
Leizorovicz A, Haugh MC, Chapuis FR, et al. Low molecular weight heparin in prevention of perioperative thrombosis. BMJ. 1992;305:913-920. [PubMed]
 
Cohen AT, Davidson BL, Gallus AS, et al. Efficacy and safety of fondaparinux for the prevention of venous thromboembolism in older acute medical patients: randomised placebo controlled trial. BMJ. 2006;332:325-329. [PubMed]
 
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