a very brief overview on randomized control trial

1. Randomized controlled trialRandomized controlled trial
Nouran Hamza, BSc Pharm, MSc,PgDPH
Biostatistician

2. Why RCTs?Why RCTs?
• The aim of RCTs is to reduce bias when testing a
new treatment.
• The people participating in the trial are randomly
allocated to either the group receiving the
treatment under investigation or to a group
receiving standard treatment (or placebo
treatment) as the control

3. Randomization ????Randomization ????
• Random allocation means that all subjects have a
defined probability of assignment to a particular
intervention
• Allocation is not predicted by the investigator,
clinicians, or subjects

4. ClassificationClassification
• Parallel-group – each subject is randomly assigned to a group, and all the
subjects in the group receive (or do not receive) an intervention.
• Crossover – over time, each subject receives (or does not receive) an
intervention in a random sequence.
• Cluster – pre-existing groups of subjects (e.g., villages, schools) are randomly
selected to receive (or not receive) an intervention.
• Factorial – each subject is randomly assigned to a group that receives a
particular combination of interventions or non-interventions (e.g., group 1
receives vitamin A and vitamin B, group 2 receives vitamin A and placebo B,
group 3 receives placebo A and vitamin B, and group 4 receives placebo A and
placebo B).

5. Parallel groupsParallel groups

6. Cross -overCross -over

7. ClassificationClassification
• By outcome of interest
• Explanatory RCTs test efficacy in a research setting with highly selected
subjects and under highly controlled conditions.
• pragmatic RCTs test effectiveness in everyday practice with relatively
unselected subjects and under flexible conditions; in this way, pragmatic RCTs
can "inform decisions about practice.

8. Efficacy vs. effectivenessEfficacy vs. effectiveness
• Efficacy
• does the intervention work in the people who
actually receive it?
• These trials tend to be explanatory
• The major aim here is high compliance
• Effectiveness
• how does the intervention work in those offered it
• Tend to be pragmatic

9. ClassificationClassification
• By hypothesis
✔ superiority trial: one treatment is superior to another,
equivalence trial: the statistical test aims at showing that✔
two treatments are not too different in characteristics in a
clinical manner.
non-inferiority design, the aim is to show that an✔
experimental treatment is not (much) worse than a
standard treatment
Clinical trials ????

10. Why blinding??Why blinding??
• To reduce detection and performance bias.
• There is evidence that lack of blinding leads to
overestimated treatment effects.

11. BLINDINGBLINDING

12. Allocation concealmentAllocation concealment
• Allocation concealed: opaque, sealed envelopes;
sealed numbered or coded bottles or containers;
• Allocation not concealed: sealed envelopes that
were not opaque, or descriptions that contain
elements lack convincing of concealment
• Unclear allocation concealment: the authors did
not report a description of an allocation
concealment

13. • Is there an association of industry sponsorship and
positive outcome in randomized controlled
trials????

14. Analysis of trialsAnalysis of trials