Long-acting beta-agonists and asthma death: how useful are different study designs to evaluate the potential association?
OBJECTIVE
There is uncertainty whether long-acting beta-agonist (LABA) drugs may increase the risk of asthma mortality. This uncertainty is partly due to the difficulty in estimating the risk of rare adverse outcomes. The aim of this paper is to consider the utility of three approaches to determine the magnitude and statistical significance of this potential association.


METHODS
Using a death rate of 9 per 10,000 subjects with asthma, derived from a meta-analysis of randomized controlled trials (RCTs) of formoterol, power calculations for a single RCT, a case-control study, and a meta-analysis of RCTs were determined.


RESULTS
For each study design, the number of subjects and events required to have adequate statistical power to detect a 1.5- and 2.0-fold increased risk of death were calculated. For a single RCT, or meta-analyses of RCTs, very large sample sizes are required. In contrast, case-control methodology represents a realistic method of estimating the risk of rare serious adverse events.


CONCLUSIONS
Major practical limitations exist in the use of RCTs to determine the potential risk of death with LABAs in the treatment of asthma. Case-control methodology may be more effective in establishing causation; however, if selection bias occurs, estimates of risk may be inaccurate.
Department of Medicine, University of Otago Wellington, Wellington, New Zealand. mark.weatherall@otago.ac.nz
Mark
M
Weatherall
Meme
M
Wijesinghe
Kyle
K
Perrin
Richard
R
Beasley
D000318:Adrenergic beta-Agonists / Q000009:adverse effects* / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy* / Q000401:mortality*; D016022:Case-Control Studies; D003692:Delayed-Action Preparations; D006801:Humans; D015201:Meta-Analysis as Topic; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D012107:Research Design
D000318:Adrenergic beta-Agonists; D003692:Delayed-Action Preparations