Patient blinding in randomized placebo-controlled trials on pharmacologic treatments for chronic pain conditions may seldom be assessed, according to a meta-analysis published in the Journal of Pain.
The medical literature was systematically reviewed to identify randomized double-blinded placebo-controlled trials that examined pharmacologic treatments for chronic pain or chronic pain associated with a medical condition and published between 2006 and 2016. A total of 408 studies (n=103,983) were selected.
Several factors were identified as predictors of a reduced likelihood of blinding assessment: a large sample size (odds ratio [OR], 0.95; 95% CI, 0.91-0.99; P =.02); referring to any version of the Consolidated Standards of Reporting Trials statement (OR, 0.29; 95% CI, 0.09-0.94; P =.03); receiving full pharmaceutical sponsorship vs no pharmaceutical sponsorship (OR, 0.21; 95% CI, 0.07-0.61; P =.004); trials on osteoarthritis vs chronic low back pain (OR, 5.96; 95% CI, 1.24-28.59; P =.03), vs pelvic pain (OR, 7.95; 95% CI, 1.30-48.76; P =.03), and vs complex regional pain syndrome (OR, 53.00; 95% CI, 8.80-319.33; P <.001).
Study limitations include the low number of studies analyzed (n=23).
“We recommend that all researchers conducting [randomized clinical trials] for chronic pain include a forced choice assessment of blinding (ie, no don’t know’ option) and report these results when publishing the data,” the investigators wrote. “Importantly, however, failed blinding should not be taken to inherently reflect a biased trial, given that failed blinding can occur because of a large observed treatment effect.”
Colagiuri B, Sharpe L, Scott A. The blind leading the not so blind: a meta-analysis of blinding in pharmacological trials for chronic pain [published online September 21, 2018]. J Pain. doi:10.1016/j.jpain.2018.09.002