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To the Editor: Dr Sin and colleagues¹ appear to have double-counted participants in 2 reported trials of tiotropium. Figure 2 of their article suggests that each tiotropium trial was treated independently. In actuality, Brusasco et al² appeared to report the combined results of Donohue et al³ and another unpublished trial, and Vincken et al⁴ appeared to report the combined results from van Noord et al⁵ and a separate unpublished trial. The total number of patients randomized in the cited trials was therefore 2663, not 3574 as stated in the article. Neither of the composite trials referenced the earlier publications with which they had overlapping participants.

Our current work on a systematic review of tiotropium⁶ for the Cochrane Collaboration suggests that this double counting did not affect the statistical significance of the findings for tiotropium, but it did make the reported results appear overly precise.

R. Graham Barr, MD, DrPH
rgb9@columbia.edu
Division of General Medicine
Columbia-Presbyterian Medical Center
New York, NY

1. Sin DD, McAlister FA, Man SFP, Anthonisen NR. Contemporary management of chronic obstructive pulmonary disease: scientific review. JAMA. 2003;290:2301-2312. FREE FULL TEXT 2. Brusasco V, Hodder R, Miravitlles M, Korducki L, Towse L, Kesten S. Health outcomes following treatment for six months with once daily tiotropium compared with twice daily salmeterol in patients with COPD. Thorax. 2003;58:399-404. FREE FULL TEXT 3. Donohue JF, van Noord JA, Bateman ED, et al. A 6-month, placebo-controlled study comparing lung function and health status changes in COPD patients treated with tiotropium or salmeterol. Chest. 2002;122:47-55. FREE FULL TEXT 4. Vincken W, van Noord JA, Greefhorst AP, et al. Improved health outcomes in patients with COPD during 1 yr's treatment with tiotropium. Eur Respir J. 2002;19:209-216. FREE FULL TEXT 5. van Noord JA, Bantje TA, Eland ME, Korducki L, Cornelissen PJ. A randomised controlled comparison of tiotropium and ipratropium in the treatment of chronic obstructive pulmonary disease: the Dutch Tiotropium Study Group. Thorax. 2000;55:289-294. FREE FULL TEXT 6. Barr RG, Bourbeau J, Camargo CA Jr, Ram FSF, Cochrane Airways Group. Inhaled tiotropium for stable chronic obstructive pulmonary disease [Cochrane Review on CD-ROM]. Oxford, England: Cochrane Library, Update Software; 2002; issue 3.

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;291:1066-1067.

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