L77 - Clinical Trials in Respiratory Disease: Critical Appraisal

Question 1

What level of evidence is a systematic review of RCTS

Answer 1

Level 1

Question 2

What level of evidence is a randomised controlled trial

Answer 2

Level 2

Question 3

What level of evidence is a Pseudo-randomised controlled trial (i.e. alternate allocation)

Answer 3

3-1

Question 4

What level of evidence is a comparative study trial with concurrent controle (i.e. non randomised clinical trial, cohort study, case control study

Answer 4

3-2

Question 5

What level of evidence is a comparative study with historical controls (i.e.single arm clinical trial)

Answer 5

3-3

Question 6

What level of evidence is a case series?

Answer 6

Level 4

Question 7

What is the clinical Setting?
P
I
C
O
T

Answer 7

Population
Intervention
Comparator/Control
Outcome
Timng

Question 8

What is Internal Validity

Answer 8

Extent to which the results of the study are valid (accurate, robust etc) for the sample of patients being studied?
Did the study answer the question it set out to answer?
Dependent on appropriate study design, data collection, and data analyses

Question 9

What is blinding?

Answer 9

Non-awareness of intervention allocation

Question 10

Single Blind

Answer 10

Subjects are unaware

Question 11

Double blind

Answer 11

Subjects and investigators are unaware

Question 12

Triple Blind

Answer 12

Subjects, investigators, and outcome assessors are unaware

Question 13

How can you reduce selection bias?

Answer 13

Randomisation

Question 14

How can you reduce information bias?

Answer 14

Blinding

Question 15

What is information bias?

Answer 15

Prejudice about the intervention can influence the outcome or its ascertainment.

Question 16

What is Objective Outcome Ascertainment?

Answer 16

Outcomes are determined according to strict, standardised, objective criteria

Question 17

What is the rationale of Objective Outcome Ascertainment?

Answer 17

Reduce information bias

Question 18

What is Intention-To-Treat-Analysis

Answer 18

Assume subjects remained in the group which they were randomly allocated, regardless of actual treatment received, drop-out, loss to follow up or cross over

Question 19

What is the rationale of Intention-To-Treat Analysis

Answer 19

Reduce Selection Bias

Question 20

What is the effect of the Intention to Treat Analysis?

Answer 20

Under estimates the treatment effect (i.e. provides a conservative estimate)

Question 21

Why does Intention-To-Treat Analysis under-estimate the treatment effect?

Answer 21

Less treatment in intervention group than assumed.

More treatment in control group than assumed?

Question 22

What do narrow and and wider confidence intervals indicate?

Answer 22

Wider CIs result from a smaller sample size and give a less precise result.

Narrower CIs result from a larr sample size and give a mroe precise result.

Question 23

What is a type 1 Error?

Answer 23

False Positive

You conclude there is a difference between your two groups when there isn’t.

A man who is not pregnant is told he is pregnant.

Question 24

What is a type 2 error?

Answer 24

False negative

You conclude there is no difference between the groups when there is

A woman who is pregnant is told she is not pregnant?

Question 25

What is an explanation for non-statistically significant results?

Answer 25

Lack of Power

Question 26

Number needed to Treat

Answer 26

NNT = 1/(absolute risk)

The number of people needed to undergo the treatment in order to prevent outcome.

Question 27

What affects the Number Needed to Treat (NNTT)

Answer 27

Relative effect (often a constant)
Underlying likelihood of the outcome.

Question 28

External validity

Answer 28

How applicable are the results of the general population?

Participants are often excluded for a number of reasons, i.e. kidney issues, likelihood of adherence etc