Abstract
Patient blinding is a critical feature of double-blind placebo-controlled randomized
controlled trials (RCTs). Yet, very little is known about practices for assessing
and reporting blinding in chronic pain trials. We examined the rates and predictors
of assessing blinding and its success in pharmacological RCTs for chronic pain. Four-hundred
eight trials (n = 103,983 participant) were identified via a systematic search between
2006 and 2016. Only 23 RCTs (5.6%) reported assessing patient blinding. Larger sample
size, reference to a CONSORT statement, and pharmaceutical sponsorship were associated
with lower rates of assessing blinding. A meta-analysis of the available data using
Bang's Blinding Index indicated that blinding was not successful when combined across
studies (g = 1.12, 95% confidence interval .92–2.01). Moderator analysis revealed
that higher rates of adverse events and larger treatment effect sizes were associated
with worse blinding outcomes, whereas including “don't know” responses seemed to improve
blinding. Overall then, blinding is rarely reported and often fails in RCTs of pharmacological
interventions for chronic pain. To address this finding, we recommend that all researchers
conducting RCTs for chronic pain assess and report on the status of patient blinding
when reporting the trial outcome.
Perspective
This meta-analysis examined patient blinding in pharmacological RCTs of chronic pain.
The results indicated that blinding is rarely assessed and often fails. Some study
characteristics were associated with lower rates of assessing blinding and its success,
for example, pharmaceutical sponsorship and side effects. Implications and recommendations
for chronic pain RCTs are discussed.
Keywords
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Article info
Publication history
Published online: September 21, 2018
Footnotes
This research was supported by Australian Research Council Discovery Project Grant (DP150104026) awarded to B.C. and L.S. and Australian Research Council Discovery Early Career Research Award (DE160100864) awarded to B.C.
The authors have no conflict of interest in producing this research.
Supplementary data accompanying this article are available online at www.jpain.org and www.sciencedirect.com.
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© 2018 by the American Pain Society
