Lecture 14: Evidence Evaluation: Experimental Studies

Question 1

What is the big picture for experimental epidemiology

Answer 1

Is there a relationship (causation)
Exposure -> outcome

Question 2

What do experimental studies evaluate?

Answer 2

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]

Question 3

How do experimental studies create a controlled environment?

Answer 3

Create a controlled environment such that the only thing
that is different between study groups (exposed/comparison) is the exposure itself

Question 4

What are Randomized Controlled Trials (RCTs)

Answer 4

Experimental study to assess the efficacy of an intervention in humans

Question 5

What is efficacy?

Answer 5

Efficacy = ability to achieve a desired effect (under highly
controlled conditions)

Question 6

What is effectiveness?

Answer 6

Effectiveness = do interventions work in circumstances that reflect
real-world practice

Question 7

What is generalizability?

Answer 7

Who can findings apply to

Question 8

What is inclusion and exclusion criteria? Broad vs Restricted

Answer 8

Inclusion and exclusion criteria to identify participants
* Broad -> Exclude few, more generalizable
* Restricted -> Exclude many, less generalizable

Question 9

What is randomization?

Answer 9

Allocation to study groups (exposed group vs. comparison group) is by chance alone

Question 10

Randomization optimizes?

Answer 10

the equal distribution of measured characteristics between
study groups

Question 11

Randomization increases the likelihood that?

Answer 11

that unmeasured characteristics are
equally distributed between study groups

Question 12

Random assignment equitably ensure that

Answer 12

every eligible participant has the same chance of receiving the intervention, free of subjective criteria or influence (by researchers)

Question 13

When does protecting randomization happen?

Answer 13

before participants are entered into a trial
* Researcher does not know if the next participants will get
treatment or control

Question 14

If concealment of allocation is not done, what does it result in?

Answer 14

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

Question 15

Is concealment of allocation always feasible in an RCT?

Answer 15

Yes

Question 16

What is blinding

Answer 16

Masking of the allocation after randomization of participants

Question 17

Is blinding feasible in all RCTs?

Answer 17

Not feasible in all RCTs (e.g. cannot blind in RCT of coffee and ileus)
but important in RCTs involving comparison to placebo

Question 18

What is single-blinded?

Answer 18

Patient does not know which study group they are allocated to

Question 19

What is double-blinded?

Answer 19

Patient and researcher do not know which study group patients are allocated to

Question 20

Why do we define all aspects of study treatment?

Answer 20

So uniform
Control
* Placebo
* Best to define efficacy of study therapy
* May not be ethical, practical, feasible
* Active control (current standard)

Question 21

What are the outcomes in an experimental study?

Answer 21

What do you want to achieve with the new intervention
* Primary endpoint
* Secondary, additional endpoints

Question 22

What are approaches to analyzing RCTs?

Answer 22

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

Question 23

What is measure of association for RCT?

Answer 23

Relative risk

Question 24

What are disadvantages of RCTs?

Answer 24

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