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British Thoracic Society, London, UK
Correspondence to: Andrew Miller, MD, FCCP, Mayday University Hospital, Croydon Chest Clinic CR7 74E, UK; e-mail: andrew.miller{at}mayday.nhs.uk
To the Editor:
Like numerous physicians, we always look forward to seeing the latest American College of Chest Physicians guidelines on antithrombotic therapy, and the latest (Seventh) edition is of the same superb quality as its predecessors. For several years,1 the British Thoracic Society has advised that 3 months of therapy is sufficient for the first episode of pulmonary embolism, including idiopathic cases, whereas our North American colleagues have interpreted the same available data to conclude that the traditional 6-month approach is preferable. This difference of opinion partly arose because, until recently, the only relevant studies included a high proportion of patients with deep vein thrombosis alone.
As members of the British Thoracic Society working party who recently updated our guidelines,2 we understood that the issue had been resolved by an excellent large multicenter study3 that only recruited patients with a first episode of proven clinical pulmonary embolism, and showed that continuing warfarin beyond 3 months merely deferred proven recurrence, both in idiopathic cases and in patients with a temporary risk factor (interestingly, the same group4 had previously reached similar conclusions in deep vein thrombosis). The interpretation of this is that in such cases there are only two logical alternatives: (1) stop at 3 months, but review in the event of a proven recurrence; or (2) use lifelong treatment, but review in the event of a significant iatrogenic bleed.
This important study was analyzed by the six international experts, one of whom was Professor Agnelli himself. For first-episode idiopathic pulmonary embolism, an option that can be "considered" (Recommendation 5.1.3 - Grade 2A) is indefinite treatment, the same as (2) above. However, we were very surprised that, for such cases, their preference ("we recommend") is "at least 6 to 12 months" (Recommendation 5.1.2). Can the latter really still be considered Grade 1A? Why is there no recommendation for 3 months, which should certainly justify the same grade as that proposed?
Leaving out such guidance means that patients will receive anticoagulation for much longer than the evidence suggests, which is inconvenient and expensive. More worryingly, there will be some (not many, but some) patients who will experience a catastrophic bleed due to treatment unnecessarily prolonged beyond 3 to "at least 6 to 12 months" as a result of this selective advice.
Could we please be enlightened?
Footnotes
The authors have no conflicts of interest to disclose.
The authors have no conflicts of interest to disclose.
References
University of Oklahoma Health Sciences Center, Oklahoma City, OK University of Amsterdam, Amsterdam, the Netherlands
Correspondence to: Gary E. Raskob, PhD, College of Public Health, University of Oklahoma Health Sciences Center, 801 NE 13th Street, Room 139, Oklahoma City, OK 73104
To the Editor:
We appreciate the comments of Dr. Miller and colleagues, and also the efforts of the British Thoracic Society. Our recommendations were developed using the following key principles: a transparent link to the strength of the relevant evidence, evaluation of the balance between risks and benefits, and explicit identification of the underlying values and preferences.1 Our recommendation that patients with a first episode of idiopathic pulmonary embolism receive treatment for 6 to 12 months was supported by the aggregate evidence available at the time for patients with idiopathic venous thromboembolism.2345 This evidence supported three conclusions: (1) stopping treatment at 3 months resulted in a high incidence of recurrent thromboembolism, (2) an extended duration of anticoagulant treatment was effective for preventing recurrent thromboembolism while patients continued therapy, and (3) the optimal duration of anticoagulant therapy remained uncertain. The study by Professor Agnelli and colleagues4 in patients with pulmonary embolism did not include sufficient patients with idiopathic pulmonary embolism to definitively conclude that 1 year of treatment was not more effective than 3 months, since the 95% confidence interval for the relative risk of recurrent thromboembolism in this subgroup ranged from 0.45 to 2.16. A similar conclusion applied to the study by Pinede and colleagues,5 in which the 95% confidence interval for the relative risk of recurrent venous thromboembolism for 6 months vs 3 months of treatment ranged from 0.47 to 1.87 in the subgroup with idiopathic venous thromboembolism. The aggregate evidence available at the time, and particularly the study by Kearon et al,2 suggested strongly that 3 months was an insufficient duration of treatment for idiopathic venous thromboembolism. We therefore recommended treatment for at least 6 to 12 months (grade 1A), providing the clinician some flexibility to tailor the duration of treatment to the patient’s specific clinical situation. We also made a separate recommendation to consider patients with idiopathic venous thromboembolism for indefinite anticoagulant treatment (grade 2A).6 Finally, we also included an explicit statement of the values and preferences underlying our recommendation, namely, "This recommendation ascribes a relatively high value to preventing recurrent thromboembolic events and a relatively low value on bleeding and cost."6 Therefore, by including this explicit statement, we acknowledged that our recommendation was weighted toward preventing recurrent thromboembolism, and that clinicians may select a shorter duration of treatment, such as 3 months, for those patients who place a relatively higher value on avoiding bleeding than on preventing recurrent thromboembolism.
References
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