Randomised Controlled Studies Flashcards
What is a clinical trial
A clinical trial is an experiment in which a treatment is administered to humans in order to evaluate its efficacy and safety
What are the types of clinical trial
- An uncontrolled trial
- A controlled trial
- A randomised controlled trial
What happens in an uncontrolled trial
– Everyone gets the treatment – used that so all participants without the treatment in the trial will die in a few months
What happens in a controlled trial
– A treated group is compared with an untreated group (placebo)
– Or a treated group is compared with a control group having “usual treatment”
– Controls may be geographical, historical, or randomised;
How is allocation determined in a randomised trial
– Allocation to groups is determined by chance
What is a geographical control and what is it subjected to
- Patients with the same disorder seen at another hospital or clinic where the new intervention is not provided
- Selection bias – patients might be more likely to die in that area anyway not necessarily due to the treatment or lack of treatment
What is a hospital control and what is it subjected to
- Patients with the same disorder seen in the past before the use of the new intervention
- Similar problem as with geographical controls (selection bias)
- More biased to therapy being better
- Can be used if outcome of standard treatment (or no treatment) are well known and vary little for a given patient population
What are the two types of controls
Geographical control
Hospital control
What is an allocation bias
Allocation bias can be defined as bias that arises from a systematic difference in how participants are assigned to treatment groups and comparison groups in a clinical trial
e.g. allocation bias may result if investigators know or predict which intervention the next eligible participant is supposed to get
What is a selection bias
Selection bias is the bias introduced by the selection of individuals, groups or data for analysis in such a way that proper randomization is not achieved, thereby ensuring that the sample obtained is not representative of the population intended to be analyzed
e.g. Examples of sampling bias include self-selection, pre-screening of trial participants, discounting trial subjects/tests that did not run to completion and migration bias by excluding subjects who have recently moved into or out of the study area
Why can you not use alternative allocation in a randomized control study
You cannot do alternate allocation as the clinicians and patients can predict the treatment to be received therefore it is not random
How was the first trial randomised
Patients randomly allocated to receive streptomycin or bed rest
each centre allotted a numbered series of envelopes, each containing a card indicating ‘S’ or ‘C’. Numerical order of envelopes based on a series of random numbers. When patient approved for trial the next envelope was opened
What are the benefits of randomised control studies
- Proper randomisation helps ensure group receiving treatment A is similar to group receiving treatment B
- Avoids selection/allocation bias
- The only systematic difference between treatment and control groups is the treatment (hopefully (doesn’t guarantee it))
what do patients have need to be before randomised
Patients need to have been deemed eligible and meet the inclusion criteria and consented to participate for a randomised control study
What are the two different types of blinding
single blind
double blind
What is a single blind trial
Single blind – patients do not know what treatment they are on but researchers do
What is a double blind trial
Double blind – also the observers do not know what treatment the patients are on (not always possible)and the patients do not know what treatment they are on
What does blinding ensure
• Ensures use of other potential treatments/ assessment of outcome/decision to withdraw patient not influenced by clinician’s or patient’s knowledge of treatment
What are the two different types of randomised controlled trials
- Parallel groups
- Crossover
describe the parallel group type of the randomised controlled trials
randomise participants into group A and group B
- give them the different treatments and then follow them up and record the outcome
describe the crossover types of randomised controlled trials
- Patients are randomised into two groups, group A and Group b
- they are given the first treatment and then the outcome is recorded
- then they are swapped and given the different treatment and then the outcome is reordered
when is the parallel type of randomised controlled trials used
Parallel group – when effect of treatment is not reversible
When is the crossover type of the randomized controlled trials used
- Cross-over – when effect of treatment is reversible
