Common RCT Designs
Parallel-Group Trial
- Participants remain in one assigned group throughout the study.
- Most common design.
Crossover Trial
- Each participant receives both interventions in sequence.
- Each participant serves as their own control.
- Requires a washout period.
- Appropriate for stable chronic conditions.
- Avoid when:
- Disease changes rapidly
- Treatment has permanent effects
- Carryover effects are likely
Factorial Trial
- Tests ≥2 interventions simultaneously.
- Example: drug A/placebo combined with drug B/placebo.
Cluster-Randomized Trial
- Randomizes groups, eg, clinics or communities.
- Useful when individual randomization would cause contamination.
- Analysis must account for correlation among people within each cluster.
Ethical Governance & Oversight
- Clinical Equipoise:
- Mandatory prerequisite: Genuine uncertainty within the medical community regarding whether the new intervention is superior to the control.
- Institutional Review Board (IRB):
- Independent body ensuring protection of human subjects, informed consent validity, and favorable risk-benefit profiles prior to and during trials.
- Data and Safety Monitoring Board (DSMB):
- Independent external committee auditing ongoing interim safety and efficacy data. c
- Empowered to terminate a trial early for:
- Unexpected toxicity/harm (safety endpoint breached).
- Overwhelming, undeniable superiority of intervention (unethical to withhold from control arm). c
- Futility (statistically impossible to achieve target efficacy endpoint).