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Correspondence
Author's response to letter on number needed to treat in COPD: exacerbations versus pneumonias
  1. Samy Suissa
  1. Correspondence to Prof Samy Suissa, Department of Epidemiology and Biostatistics, Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital, McGill University, 3755 Cote Ste-Catherine, H-461, Montréal, Québec, Canada H3T 1E2; samy.suissa{at}mcgill.ca

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I thank Keene et al for their letter.1 I am pleased to clarify the issues they have raised about my paper.2 First, I agree that when dealing with recurrent events such as exacerbations, it is statistically more informative to analyse all events with tools such as incidence rates and rate differences. The point of my paper, however, was that inverting these rate differences and calling the result a number needed to treat (NNT) is simply wrong. For example, while the rates of chronic obstructive pulmonary disease (COPD) exacerbation from the TORCH trial are valid representations of …

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Footnotes

  • Competing interests The author has received research grants and/or participated in advisory meetings or as conference speaker for AstraZeneca, Boehringer-Ingelheim, Forest, GlaxoSmithKline, Merck, Novartis, Nycomed and Pfizer.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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