EBM - Therapy Article

Question 1

Which level of evidence is the strongest?

Answer 1

Meta-analysis

Question 2

Rank levels of evidence from strongest to weakest

Answer 2

1. Meta-analysis
2. Systematic reviews of RCT
3. Randomized Control Trial (RCT)
4. Cohort studies
5. Case-control studies
6. Individual case reports
7. Expert opinon or physiology based

Question 3

Randomized Control Trials

Answer 3

• Subjects are randomized to groups
• Concealment, also called blinded, such that the neither the patients nor the investigator knows which group the subject is in.

Question 4

Is the evidence of the therapy valid? (questions to ask)

Answer 4

• Was the assignment of patients to treatment randomized?
• Was the randomization concealed?
• Were the groups similar at the start of the trial?
• Was follow-up of patients sufficiently long and complete?
• Were all patients analyzed in the groups to which they were randomized?
• Were patients, clinicians, and study personnel kept blind to treatment?
• Were groups treated equally, apart from the experimental therapy?

Question 5

What is the magnitude of the treatment effect?

Answer 5

This is the difference between the two treatment groups.

Question 6

In a randomized controlled trial, the magnitude is…

Answer 6

where the treatment is compared to a placebo control, the results are usually recorded as relative risk, relative risk reduction, or hazard ratios.

Question 7

In a non-inferiority trial, the magnitude is…

Answer 7

the results are presented as comparisons of the CI between the control (standard) drug and the experimental drug

Question 8

“How precise is the estimate of the treatment effect?” What measures this?

Answer 8

This is the 95% Confidence Interval

*The more narrow, the more precise

Question 9

When the endpoints of a study are reported as HR, we know that the HR represents…

Answer 9

a ratio of survival or some bad outcome at some specific time in the study

Question 10

Odds definition

Answer 10

A ratio of the number of people incurring an outcome event to the number of people who don’t have an event

Question 11

Define odds ratio

Answer 11

The ratio of the odds of having the target disorder in the experimental group relative to the odds in favor of having the target disorder in the control group. (used in cohort studies or systemic reviews)

Or…

Question 12

Define odds ratio

Answer 12

The odds in favor of being exposed in participants with the target disorder divided by the odds in favor of being exposed in the control participants (without the target disorder)

Question 13

Formula for odds

Answer 13

Odds = Probability / 1-probability

When probability is 80%
0.80/1– 0.80/0.20 = 4

Question 14

Formula for probability

Answer 14

Probability = Odds / 1+ Odds

When odds are 4,
4/1+ 4 = 0.80 or 80%

Question 15

What is a non-inferiority trial?

Answer 15

Comparing a new drug to a standard of care drug.

Question 16

How are results presented in a non-inferiority trial?

Answer 16

presented as comparisons of a predetermined “margin” and the lower limits of the 95% CI of the difference between the two drugs.

Question 17

“Are the results applicable to our patient?” What questions should we consider?

Answer 17

• Is our patient so different from those in the study that its results cannot apply?
• Is the treatment feasible in our setting?
• What are our patient’s potential benefits and harms from the therapy?
• What are our patient’s values and expectations for both the outcome we are trying to prevent and the treatment we are offering?