Placebo-Controlled
Definition
A design in which the comparison arm receives placebo rather than nothing or another active agent, isolating the intervention's own contribution to whatever changed.
Terms used in this definition
Other entries this definition refers to.
What this means for research sourcing
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Related Terms in Evidence & Research
Placebo Effect
Improvement that follows the expectation of treatment rather than the treatment itself. It is real, measurable and occasionally large, and separating it from a drug effect is the entire purpose of a control arm.
Crossover Trial
A design in which each participant receives both treatments in sequence with a washout between, so each person acts as their own control. It needs fewer participants and only suits stable, reversible conditions.
Intention-to-Treat
Analysing every participant in the arm they were randomised to, whether or not they finished. It preserves the randomisation and usually gives a more conservative answer than analysing completers only.
Endpoint
A defined, measurable outcome a trial uses to judge an intervention. Which endpoints were chosen, and when, is as informative as the results reported against them.
Primary Endpoint
The single outcome a trial was designed and powered to answer, fixed before data collection. Secondary endpoints are informative and are not what the trial succeeded or failed on, a distinction that press releases regularly blur.
Biomarker
A measurable indicator standing in for a process, a disease state or a response. Serum IGF-1 is the usual biomarker in growth hormone secretagogue work, and a biomarker moving is not the same as an outcome improving.
HbA1c (Glycated Hemoglobin)
A blood measure reflecting average glucose over roughly the preceding two to three months, reported as a percentage. It is the standard primary endpoint in metabolic trials, which is why a result quoted in points of HbA1c appears in almost every incretin paper.
Effect Size
How large the difference an intervention produced actually was, in real units or as a standardised measure. Once significance is established this is the only question left that matters.