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Jacques Rizkallah, MD; Don D. Sin, MD, FCCP
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University of British Columbia Vancouver, BC, Canada

Don D. Sin, MD, FCCP, University of British Columbia, James Hogg iCapture Center, St. Pauls Hospital, Room 368A, 1081 Burrard St, Vancouver BC, Canada V6Z 1Y6; e-mail: dsin@mrl.ubc.ca


The authors have 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(2):645-646. doi:10.1378/chest.09-0912
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To the Editor:

We thank Dr. Simons and colleagues for pointing out the limits of our metaanalysis. The studies that were included in the review generally excluded patients who had an infectious source for their acute exacerbation. Thus, the results of the metaanalysis should be generalized only to cases in which an infectious etiology for the exacerbation has been carefully ruled out.1 While we agree with Dr. Simons and colleague's general comments, we have concerns regarding their use of vague and inappropriate epidemiologic terminology, which obfuscate rather than facilitate discourse on this matter. First, contrary to Dr. Simons and colleague's assertion, there was no selection bias. The selection of the studies for the present metaanalysis was transparent, inclusive, and consistent with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) Guidelines.2 The primary studies excluded patients with an infectious etiology, which as stated previously, limits the generalizability but not the validity of the findings. Second, there was no “inadequate study sampling.” We did not sample studies; we included all published studies that met the a priori inclusion and exclusion criteria. Third, there was no “exclusion of patient categories.” We did not exclude patients or studies based on categories such as age, sex, race, lung function, or any other variables.

In sum, the concerns raised by Dr. Simon and colleagues are not justified. Nevertheless, we believe (as Dr. Simon and colleagues do) that the prevalence of venous thromboembolic (VTE) disease in acute exacerbations of COPD remains open to debate not because of the inherent methodologic biases of the present metaanalysis but because of the paucity of large, well-conducted multicenter studies that have examined this issue. Until such studies are conducted, the present metaanalysis suggests that clinicians should keep a high index of suspicion for VTE disease in patients who are hospitalized with acute COPD exacerbation and in whom an infectious source has been clinically ruled out.

Rizkallah J, Man SF, Sin DD. Prevalence of pulmonary embolism in acute exacerbations of COPD: a systematic review and metaanalysis. Chest. 2009;135:786-793. [PubMed] [CrossRef]
 
von Elm E, Altman DG, Egger M, et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007;370:1453-1457. [PubMed]
 

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Rizkallah J, Man SF, Sin DD. Prevalence of pulmonary embolism in acute exacerbations of COPD: a systematic review and metaanalysis. Chest. 2009;135:786-793. [PubMed] [CrossRef]
 
von Elm E, Altman DG, Egger M, et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007;370:1453-1457. [PubMed]
 
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