Duke Health - Module 3

Question 1

Three overarching questions

Answer 1

1. How serious is the risk of bias?
2. What are the results?
3. Will the results help in caring for my patient?

Question 2

Were patients randomized?
* The assignment or patients to either group (treatment or control) must be done by

Answer 2

a random allocation

Question 3

Were patients randomized?
* The assignment or patients to either group (treatment or control) must be done by a random allocation
* This might include:
(2)

Answer 3

o A coin toss
o Computer generated randomization tables

Question 4

• Randomization balances the groups for …

This reduces the chance of …

Answer 4

known prognostic factors (such as age, weight, gender, etc.) and unknown prognostic factors (such as compliance, genetics, socioeconomics, etc.).

over-representation of any one characteristic within the study groups.

Question 5

Was group allocation concealed?
* The randomization sequence should be concealed from the clinicians and researchers of the study to further eliminate

Answer 5

conscious or unconscious selection bias.

Question 6

• Concealment, which is part of the enrollment process, ensures that

Answer 6

the researchers cannot predict or change the assignments of patients to treatment groups

Question 7

• If allocation is not concealed it may be possible to influence the outcome consciously or unconsciously by changing:
  (2)

Answer 7

o The enrollment order
o The order of randomly assigned treatment

Question 8

• Concealed allocation can be done by using
  (2)

Answer 8

o A remote call center for enrolling patients
o The use of opaque, sealed envelopes with assignments

Question 9

• This is different from blinding which happens — randomization

Answer 9

AFTER

Question 10

Were patients in the study groups similar with respect to known prognostic variables?
* The treatment and the control groups should be similar for all prognostic characteristics except …
* A good way to verify that randomization results in similar groups is to reference a …

Answer 10

whether or not they received the experimental treatment

Baseline Characteristics Table

Question 11

• Blinding means that

Answer 11

people involved in the study do not know which treatments were given to which patients. Patients, researchers, data collectors and others involved in the study should not know which treatment is being administered

Question 12

• This helps eliminate (2)

Answer 12

assessment bias and preconceived notions as to how the treatments should be working

Question 13

• When it is difficult or even unethical to blind patients to a treatment, such as a surgical procedure, then …

Answer 13

a “blinded” clinician or researcher is needed to interpret the results

Question 14

• The study should begin and end with

Answer 14

the same number of patients in each group. Patients lost to the study must be accounted for or risk making the conclusions invalid

Question 15

o Patients may drop out because of the — of the therapy being tested
o If not accounted for, this can lead to conclusions that may be …

Answer 15

adverse effects

overly confident in the efficacy of the therapy

Question 16

• Good studies will have better than –% follow up for their patients. When there is a large loss to follow-up, the lost patients should be assigned to the “—” outcomes and the results recalculated. If these results still support the original conclusion of the study, then the loss may be acceptable

Answer 16

80
worst-case

Question 17

Were patients analyzed in the groups to which they were first allocated?
* Anything that happens after randomization can affect the chances that a patient in a study has an —
* Patients who forget or refuse their treatment should not be …
* Excluding noncompliant patients from a study group may leave only those that may be more likely to have a positive outcome, thus compromising the unbiased comparison that we got from the process of randomization. Therefore …

Answer 17

event
eliminated from the study results or allowed to “change groups.”
all patients must be analyzed within their assigned group.

Question 18

• Randomization must be preserved. This is called “—” analysis

Answer 18

intention to treat

Question 19

• Stopping trials early when one sees an apparent large benefit or because of a perceived harm to participants is risky
• One of the main reason is that these truncated RCTs can

Answer 19

greatly overestimate the treatment benefit, particularly in trials with small sample sizes

Question 20

When we review the results, we typically ask how large and precise was the treatment effect
* We want to balance the (2) of the treatment effect with a consideration of — significance versus — significance

Answer 20

size and precision
clinical, statistical

Question 21

o Experimental event rate (EER):

Answer 21

outcome present/total in experimental group

Question 22

o Control event rate (CER):

Answer 22

outcome present/total in control group

Question 23

o Absolute benefit increase (ABI):

Answer 23

the arithmetic difference between the rates of events in the experimental and control group. Refers to the increase of a good event as a result of the intervention
 EER - CER

Question 24

o Relative risk (RR):

Answer 24

the ratio of the risk in the experimental group compared to the risk in the control group. Proportional reduction in risk between the rates of events in the control group and the experimental group
 EER / CER

Question 25

o Relative benefit increase (RBI):

Answer 25

the proportional increase in benefit between the rates of events in the control group and the experimental group
 ABI / CER

Question 26

o Numbers needed to treat (NNT):

Answer 26

the number (rounded to the nearest whole) of patients who need to be treated to prevent one bad outcome or produce one good outcome
 1 / ABI

Question 27

How precise was the treatment effect?
* We usually use the –% CI

Answer 27

95

o You can consider the 95% CI as defining the range that, assuming the study has low risk of bias, includes the true treatment effect 95% of the time

Question 28

• Clinical significance has little to do with statistics and is a matter of —

Answer 28

judgement

Question 29

• Clinical significance often depends on the

Answer 29

magnitude of the effect being studied and answers the question

Question 30

• Studies can be statistically significant yet

Answer 30

clinically insignificant

Question 31

Once we have determined the risk of bias and interpreted the results, we can ask how we will apply the results to patient care
* We ask..
(3)

Answer 31

o Were the study patients similar to my population of interest?
o Were all clinically important outcomes considered?
o Are the likely treatment benefits worth the potential harms and costs?