Elsevier

Respiratory Medicine

Volume 101, Issue 6, June 2007, Pages 1313-1320
Respiratory Medicine

External validity of randomized controlled trials in COPD

https://doi.org/10.1016/j.rmed.2006.10.011Get rights and content
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Summary

Background

COPD is a heterogeneous disease comprising a wide range of clinical phenotypes, depending on the degree to which emphysema, chronic bronchitis, reversible bronchospasm and small airways inflammation are present. Not all of these phenotypes may be represented among the subjects included in randomized controlled drug trials (RCTs) in COPD, making it difficult for doctors to know to what extent RCT evidence applies to individual patients. From a respiratory health survey of adults randomly selected from the community, we have estimated the proportion of subjects with COPD who would have been eligible for inclusion in major COPD RCTs.

Methods

A postal survey was sent to 3500 randomly selected individuals aged 25–75 years. Respondents were invited to complete a detailed respiratory questionnaire and pulmonary function tests. Subjects with COPD defined by post-bronchodilator spirometry were assessed against the eligibility criteria of 18 major RCTs cited in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines.

Findings

Of 749 subjects completing the full survey, 117 had COPD. Of these, a median of 5% (range 0–20%) of subjects met inclusion criteria for the major RCTs. Of 55 subjects with COPD receiving treatment, 0–9% (median 5%) met inclusion criteria for the major RCTs.

Interpretation

The major COPD RCTs on which the GOLD treatment guidelines are based may have limited external validity. Over 90% of the COPD subjects in the community who were taking medication, did so on the basis of RCTs for which they would not have been eligible.

Keywords

Chronic obstructive pulmonary disease
Adult
Randomized controlled trial
External validity
Inclusion criteria
Exclusion criteria

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