Randomised Control Trials Flashcards
Clinical trial
Experiment in which a treatment is administered to humans in order to evaluate its efficacy and safety
Uncontrolled trial
Everyone gets treatment
Controlled trial
Treated group compared to untreated group or group having normal treatment
Randomised controlled trial
Controlled trial with allocation to groups determined by chance
Geographical control
Pts w same disorder seen at another hospital/clinic where new intervention not provided
Historical control
Pts w same disorder seen in the past before the use of new intervention
What type of bias is introduced by the selection of individuals, groups, or data for analysis in such a way that proper randomization is not achieved, thereby failing to ensure that the sample obtained is representative of the population intended to be analyzed
Selection bias
Why is alternate allocation not used for clinical trials
Clinician/patient can predict treatment to be recieved
Benefits of randomised controls
Ensure groups being studied are similar
Avoids selection/allocation bias
Only systematic difference between treatment and control groups is the treatment
Are trial patients allocated to groups before or after being deemed eligible and consenting to the trial
After
Single blind trial
Pt doesn’t know what treatment they are on
Double blind trial
Pt and observers do not know what treatment they are on
2 types of randomised controlled trial
Parallel
Cross over
What is an AB/BA crossover study
Pts in group A and B ->1 group treated 1 not -> outcomes recorded -> groups switch which is treated and which isnt -> outcomes recorded
When are parallel trials used
When effect of treatment not reversible
When are crossover trials used
When effect of treatment is reversible
Advantages of cross over trials
Each pt is their own control
Smaller sample size needed for same nbr of observations
Useful for subjective measurements
Disadvantages of crossover trials
More time consuming
Carry over effects
How are carry over effects prevented in crossover trials
Washout period between 1st and second treatment periods
Cluster randomised trials
pre-existing groups of individuals are randomly allocated to treatment arms, eg villages, schools, gps
Factorial controlled trial
test the effect of two or more treatments simultaneously using various combinations of the treatments.
What stage of developing a drug uses in vitro and in vivo animal testing
Preclinical
Purposes of each stage of drug testing
Preclinical - preliminary efficacy, toxicity and pharmacokinetics in animals
Phase 0 - pharmacokinetics and pharmacodynamics
Phase 1 - safety
Phase 2 - efficacy and safety
Phase 3 - therapeutic effect
Phase 4 - pharmacovigilance
Advantages of trial registries
Assist in planning
Avoid research duplication
Encourage collaboration
Optimise use of funds
Incr pt access to info
Improve recruitment
Detect bias
How to calculate relative risk of death in treatment group compared to control
Risk of death in treatment/risk of death in control
Intention to treat
Comparison of all subjects based on treatment group assigned regardless of whether they complied
On treatment
Comparison of subjects who actually took treatment
How can compliance in trials be increased
Selection of patients
Double blind design
Run in period where all are treated to identify those who can’t tolerate treatment
How to calculate how many people need a treatment to prevent an event
100/ difference in risk between treatment and control groups
Purpose of meta analysis
Bring together all evidence to more powerfully estimate effect size
What type of graph are meta analysis results usually shown in
Forest plot
Issues in meta analysis
Heterogeneity in study results
Publication bias
What causes heterogeneity in study results
Different study designs
Different participant characteristics
Differences in intervention
Chance
What causes publication bias
Studies with significant/favourable results more likely to be published
