Randomised control trials

Randomised control trials

1. study type most likely to test causality

   • best able to deal with confouding factors
   • can determine the type, magnitude, frequency and duration of intervention under investigation.
   • high quality of evidence

2. types of RCT

   • efficacy vs effectiveness trials
     • does the patient require a 1kg tablet to be effective
   • superiority vs equivalence trials
     • treatement A compared to treatement B

3. Trials phases

   • Phase 1
     • adverse effects and
   • Phase 2
     • first in humans, efficacy
   • Phase 3
     • double blind RTC's on a large scale efficacy in humans
     • Clinical trials done before dug marketing
     • efficacy rather than effectiveness at this stage

4. Experimental study type

5. Advantages

   • randomisation
     • everyone has equal chance to be in the control or the study group
     • eequal distribution of known and unknown confounders
   • blinding
     • single blinding
     • double blinding
     • unbiased, independant assessors of the outcome
       • assessors nopt linked to the drug being tested etc.
   • allocation concealment
     • sequence of enrollment is "concealed" from researchers and assessors
   • primary study type with high quality evidence
   • tests hypothesis

6. must be ethical

7. Disadvantages

   • cant be done if not ethical
   • must use the current treatement if one is available as a control
   • long follow-up
     • risk of loss to follow-up
   • costly
   • not all questions can be answered
   • doesnt always mimic reality
     • patients may forget to take the treatement
     • control group may take a different treatement
     • multiple disease states - eligibility criteria

8. must use a placebo, rather than no chocolate