Randomised Controlled Trial (RCT)
A study design where participants are randomly assigned to treatment or control groups, considered the gold standard for evaluating drug efficacy. Randomisation minimises bias by ensuring differences in outcomes reflect the treatment rather than pre-existing group differences.
Technical Context
Randomisation methods include: simple randomisation (coin-flip equivalent — may produce unequal groups by chance), block randomisation (ensures equal group sizes within sequential blocks), stratified randomisation (balances key prognostic factors across groups), and adaptive/response-adaptive randomisation (adjusts allocation based on interim data). Allocation concealment ensures that the person enrolling participants cannot predict the next assignment, preventing selection bias. Control types: placebo (identical inactive treatment), active comparator (existing therapy — e.g. semaglutide Phase III trials compared to sitagliptin, empagliflozin, and insulin), and standard of care (whatever treatment the physician would normally prescribe). The choice of control affects the trial's ability to demonstrate superiority, non-inferiority, or equivalence.