Who controls the placebo? Introducing a Placebo Quality Checklist for pharmacological trials

Randomised placebo-controlled trials (RCT) are an invaluable tool for testing the efficacy of new treatment strategies. The choice of placebo in an RCT can affect not only patients' physical and psychological response to a particular intervention, but also the trial setting, the success of patient blinding to the intervention, and therefore the outcome of the study and the efficacy of treatment in general. Therefore the placebo is intrinsically tied to the trial's methodology and results. However, although placebos are an important component in randomised trials, their quality is often left unquestioned. A placebo which was not properly validated may even have specific effects that lead to false negative results. To address this deficit, we propose a measure of placebo quality using the term placebo to assess the physical aspect of a dummy treatment used in the placebo group of a randomised controlled trial (RCT). The Placebo Quality Checklist (PQC) described here may help investigators select an appropriate placebo and help both investigators and critical readers interpret the findings of studies with more care.