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Randomised controlled trials

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  • Dear mr Gaber,
    I would like to use your randomized controlled trials slides in a ouse on rsesrch methods on our MSc in Seriopus Games, Coventry University. I would use them as a basis for my own slides and mention they are inspired by yours on the title slide.
    Let me know if you have any objections to this
    best regards
    Dr Maurice Hendrix
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  • 1. Randomized controlled trials The Basics
  • 2. Definition
    • RCT is a study in which a group of investigators studies two interventions in a series of individuals who receive them in a random order.
    • Intervention to be tested is called the experimental group
  • 3.
    • The other intervention is regarded as a standard of comparison or control, and the group of participants who receive it is called the control group.
    • The control can be conventional practice, a placebo, or no intervention at all
  • 4. Schema of a simple trial Eligible patients Rx group 1 Rx group 2 Randomize
  • 5. Why Randomize?
    • Compare groups at the end of the trial
    • Difference is because of the Rx
    • For this you need comparable groups
    • Purpose of randomization is to make the treatment groups comparable
    • Ensures that only difference in groups is due to trial treatments
  • 6. RCT
    • ‘ the most powerful tool in modern clinical research “
    • Prospective
    • Controlled
    • unbiased
  • 7. What is wrong with non-randomized studies?
    • Two main types of study, those with and those without concurrent control groups
  • 8. Non-randomized studies II
    • Without concurrent controls
      • Uncontrolled
        • cannot really make much of such studies if there is any variation in outcomes.
      • Historical controls
        • type of patient may change, due to eligibility criteria
        • environment changes, due to trial
        • data quality often quite different between groups
  • 9. Non-randomized studies III
    • Non-randomized concurrent controls
      • Alternation
      • Odd/Even hospital no. or date of birth
      • First letter of surname
    • Difficult to argue that one group is different from another but allocation is predictable, so bias can arise from selection of patients
      • so randomization must be unpredictabl e
  • 10. Random allocation
    • all participants have the same chance of being assigned to each of the study groups
    • the purpose is to keep both groups as similar to each as possible at the start of the trial.
  • 11. Is coin tossing OK?
    • OK for big trials
    • For small trials, such ‘simple randomization’ can lead to imbalance in group sizes
  • 12. Example: trial with 30 patients
    • If 30 patients are in a trial randomized using coin tossing there is a 14% chance of 15:15 split
    • For 16:14 chance is 27%
    • ‘ Worse’ than 20:10 is 10%
    • Why ‘worse’?
    • Because imbalance leads to loss of power
  • 13. But we need randomization
    • to be done properly
    • to ensure similar numbers in groups
    • To combine with stratification - in large trials- to ensure comparability for prognostic factors
  • 14. Pseudo-randomisation
    • Alternating record number
    • Date of birth
    • Geographical distribution
    • Open list
  • 15. True randomization
    • Need to separate the person who generates allocation from those who assess eligibility
    • Third party schemes
        • Telephone randomization service
        • Pharmacy randomization
        • Web-based service?
    • Envelopes
        • Sealed envelopes (preferably opaque)
  • 16. Value of randomization
    • it reduces the risk of serious imbalance in unknown but important factors that could influence the clinical course of the participants.
  • 17. Types of RCTs
    • RCTs according to whether the investigators and participants know which intervention is being assessed
    • Open trials
    • Single blind trials
    • Double blind trials
    • Triple blind trials
  • 18.
    • RCTs according to how the participants are exposed to the interventions
    • Parallel trials
    • Crossover trials
    • Trials with factorial design
  • 19. Blinding
    • The best way to protect a trial against is by keeping the people involved in the trial unaware of the identity of the interventions for as long as possible
  • 20. Blinding
    • Could be single
    • Could be double
    • Could be triple
  • 21. Blinding is difficult
    • Having placebo in the same shape , formula and taste is very costly, and time consuming.
    • The drug side effects e.g. local reaction at the site of injection would partially unblind .
    • Impossible if surgical and medical treatments are compared.
    • The need for urgent unblinding code in case of serious side effects
  • 22. Follow up
    • Adherence to the study protocol
    • Patients compliance with treatment and follow up
    • sufficiently long and complete
  • 23. Analysis of clinical trials Analysis of clinical trials Intension to treat analysis Per protocol analysis Sub group analysis
  • 24. Disadvantages of RCTs
    • expensive: time and money;
    • volunteer bias;
    • ethically problematic at times.
  • 25. Interim Analysis
    • Done in large multicenter RCTs
    • To explore the results after recruiting of half of the participants
    • If marked difference is recognized , then trial should be stopped
    • Examples: WHI trial
    • Breech Trial
    • AIDS trial
  • 26. RCTs
    • The gold standard for therapeutic research
    • Basis for Meta-analysis
    • Search for it first