Randomisation
The process of randomly assigning clinical trial participants to treatment or control groups, ensuring that any differences in outcomes are attributable to the treatment rather than pre-existing differences. Computer-generated randomisation sequences are standard in modern clinical trials.
Technical Context
Modern trials use computer-generated randomisation through interactive response technology (IRT/IXRS) systems that assign treatment in real-time when a participant is enrolled. Stratified randomisation ensures balance for key prognostic factors: common stratification variables include baseline HbA1c (for diabetes trials), baseline BMI (for weight trials), geographic region, and background therapy. Block randomisation (blocks of 4-8) ensures approximately equal allocation within each stratum. Allocation concealment (the process of preventing foreknowledge of treatment assignment) is critical — sequentially numbered, sealed envelopes are the minimum acceptable method, but centralised IRT systems are the gold standard. Broken allocation concealment is the single most important source of bias in clinical trials.