Lecture 14: Evidence Evaluation: Experimental Studies Flashcards
What is the big picture for experimental epidemiology
Is there a relationship (causation)
Exposure -> outcome
What do experimental studies evaluate?
Evaluate specific intervention
* intervention can be new drug, device, health care service
* Intervention = exposure
* ‘ exposed group’ [e.g., treatment] versus ‘comparison group’ [e.g. placebo, usual care]
How do experimental studies create a controlled environment?
Create a controlled environment such that the only thing
that is different between study groups (exposed/comparison) is the exposure itself
What are Randomized Controlled Trials (RCTs)
Experimental study to assess the efficacy of an intervention in humans
What is efficacy?
Efficacy = ability to achieve a desired effect (under highly
controlled conditions)
What is effectiveness?
Effectiveness = do interventions work in circumstances that reflect
real-world practice
What is generalizability?
Who can findings apply to
What is inclusion and exclusion criteria? Broad vs Restricted
Inclusion and exclusion criteria to identify participants
* Broad -> Exclude few, more generalizable
* Restricted -> Exclude many, less generalizable
What is randomization?
Allocation to study groups (exposed group vs. comparison group) is by chance alone
Randomization optimizes?
the equal distribution of measured characteristics between
study groups
Randomization increases the likelihood that?
that unmeasured characteristics are
equally distributed between study groups
Random assignment equitably ensure that
every eligible participant has the same chance of receiving the intervention, free of subjective criteria or influence (by researchers)
When does protecting randomization happen?
before participants are entered into a trial
* Researcher does not know if the next participants will get
treatment or control
If concealment of allocation is not done, what does it result in?
If not done, results in error (“bias”) such that certain patients may be
more likely to enter into one study group over another -> lose
benefits of randomization
Is concealment of allocation always feasible in an RCT?
Yes
What is blinding
Masking of the allocation after randomization of participants
Is blinding feasible in all RCTs?
Not feasible in all RCTs (e.g. cannot blind in RCT of coffee and ileus)
but important in RCTs involving comparison to placebo
What is single-blinded?
Patient does not know which study group they are allocated to
What is double-blinded?
Patient and researcher do not know which study group patients are allocated to
Why do we define all aspects of study treatment?
So uniform
Control
* Placebo
* Best to define efficacy of study therapy
* May not be ethical, practical, feasible
* Active control (current standard)
What are the outcomes in an experimental study?
What do you want to achieve with the new intervention
* Primary endpoint
* Secondary, additional endpoints
What are approaches to analyzing RCTs?
Intention to treat analysis
* All randomized patients are included in the final data analysis
Per protocol analysis
* Only patients who complete the trial according to protocol are analyzed
What is measure of association for RCT?
Relative risk
What are disadvantages of RCTs?
Expense – typically $millions
* Time – typically years
* Only answer a single question
* May not be applicable to most patients in practice
* May not be practical, ethical
* Hard to get funded
* Time consuming and complex
