Advantages and disadvantages of randomised control study design

Advantages of randomised control trial study design:

• Comparative:
  • One treatment is directly compared to another to establish superiority.
  • This study design can make causal inferences, i.e. it is the strongest empirical evidence of a treatment's efficacy
• Minimises bias:
  • Randomisation minimises allocation bias and selection bias
  • Blinding minimises performance bias
  • Double-blinding minimises assessment bias
  • Allocation concealment minimises both performance and assessment bias\
  • Prospective design minimises recall error and selection bias
• Minimises confounding factors:
  • Randomisation minimises confounding due to unequal distribution of prognostic factors
  • Randomisation makes groups comparable according both known and unknown factors
  • Blocked randomisation makes groups comparable within known confounding factors 
• Statistical reliability
  • Statistical test of significance is readily interpretable when the study is randomised
  • Sample size - when adequately powered- avoids both Type 1 error (where the null hypothesis is incorrectly rejected) and Type 2 error (where the null hypothesis is incorrectly accepted)
• Publishable
  • Considered the gold standard: more publishable

• Logistics:
  • Power calculation might demand vast samples size, which require more resources from the investigators
  • Validity requires multiple sites, which will be difficult to manage
  • Long trial run time may result in the loss of relevance as practice may have moved on by the time the trial is published
• Statistics
  • A disadvantage of block randomization is that the allocation of participants may be predictable and result in selection bias when the study groups are unmasked
• Applicability
  • Trials which test for efficacy may not be widely applicable. Trials which test for effectiveness  are larger and more expensive
  • Results may not always mimic real life treatment situation (e.g. inclusion / exclusion criteria; highly controlled setting)
• Ethical limitations
  • Randomisation requires clinical equipoise: one cannot ethically randomise patients unless both treatments have equal support in the clinical community
  • Informed consent is often impossible
  • Some research cannot be ethically performed as an RCT (classically,  RCT of the effects of parachutes on the survival of sky-divers)