Document Detail


Statistical treatment of exacerbations in therapeutic trials of chronic obstructive pulmonary disease.
MedLine Citation:
PMID:  16439716     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Randomized trials and a meta-analysis suggesting that inhaled corticosteroids reduce exacerbation rates in patients with chronic obstructive pulmonary disease (COPD) show major discrepancies that may be due to different approaches to data analysis. These trials used statistical techniques that were either weighted or unweighted for follow-up time, with p values and confidence intervals estimated with or without accounting for between-patient variability in exacerbation rates. We illustrate the validity of these methods using data from a cohort of 5,454 patients with COPD structured to emulate a randomized trial. The "reference" group was defined as patients with a history of exacerbations before cohort entry (n=1,137), whereas the "treated" group included an equal number (n=1,137) of patients with no prior exacerbation. Random samples of 100 and 200 subjects were selected three times from each of two groups to further illustrate the variability in the findings. Exacerbations during follow-up were identified from prescriptions for systemic antibiotics. The correct rate ratio of 0.75 estimated by the weighted approach was underestimated as 0.57 by the unweighted approach. When the weighted approach did not, however, also account for between-patient variability, the p value was greatly underestimated (e.g., rate ratio, 0.79; p=0.0007 instead of p=0.12) and confidence intervals were much narrower than after properly accounting for this variability. In conclusion, the reports from randomized trials and the meta-analysis that inhaled corticosteroids reduce COPD exacerbation rates are the result of improper statistical analysis techniques. The only two studies that used the correct statistical approach found insignificant effects with these drugs.
Authors:
Samy Suissa
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review     Date:  2006-01-26
Journal Detail:
Title:  American journal of respiratory and critical care medicine     Volume:  173     ISSN:  1073-449X     ISO Abbreviation:  Am. J. Respir. Crit. Care Med.     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-04-07     Completed Date:  2006-05-16     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  9421642     Medline TA:  Am J Respir Crit Care Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  842-6     Citation Subset:  AIM; IM    
Affiliation:
Division of Clinical Epidemiology, Royal Victoria Hospital, McGill University Health Centre, Montreal, Canada. samy.suissa@clinepi.mcgill.ca
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MeSH Terms
Descriptor/Qualifier:
Clinical Trials as Topic / statistics & numerical data*
Data Interpretation, Statistical
Humans
Pulmonary Disease, Chronic Obstructive / therapy*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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