5: Critical appraisal

Question 1

What is critical appraisal?

Answer 1

Evaluating a piece of research to determine if it’s valid i.e can you trust its methods and its conclusions

Question 2

What is

a) internal
b) external

validity in relation to research?

Answer 2

a) Are the method and results sound
b) Can you apply the results of the study to real life

Question 3

What does efficacy mean?

Answer 3

Ability to produce desired result

Question 4

What does effectiveness mean?

Answer 4

Measure of an intervention’s benefit in real life

Question 5

What is the impact factor of a journal?

Answer 5

How well respected it is, doesn’t automatically mean the study will be good but good journals tend not to accept crap studies

Question 6

How does a cross-sectional study work?

Answer 6

Take a large group and use a questionnaire to split them into subgroups

Gives you an idea of risk factors and disease prevalence at a snapshot in time

Question 7

Cross-sectional studies can only measure (incidence / prevalence).

Answer 7

prevalence

Question 8

What is a case-control study?

Answer 8

Comparing two groups (disease vs control) and their exposure to a risk factor

i.e looking back to see if a certain isolated risk factor has increased the likelihood of x

Question 9

Case-control and cross-sectional studies are (retrospective / prospective).

Answer 9

retrospective

Question 10

What is a cohort study?

Answer 10

Take a group of individuals

filter into subgroups for risk factors they’re exposed to (or not)

follow subgroups over time and see how risk factors affected disease incidence

Question 11

A cohort study is (prospective / retrospective).

Answer 11

prospective

Question 12

In cohort studies, there is a risk that participants are ___ to follow-up.

Answer 12

lost

Question 13

What is the gold-standard study design for clinical trials?

Answer 13

Randomised control trial

Question 14

What does intention to treat mean in relation to randomised control trials?

Answer 14

Patient results are attributed to the group they were in initially, even if they change / stop the new intervention

Question 15

What is per protocol analysis in relation to randomised control trials?

Answer 15

Only those who finish treatment on the new intervention are analysed in the ‘new intervention’ results

Question 16

Whether you use intention to treat or per protocol analysis will change the study’s ___.

Answer 16

results

Question 17

Which analysis method for RCTs (intention to treat or per protocol) is more accurate?

Answer 17

Intention to treat

Per protocol tends to make the new intervention look better, as you’re cutting out the patients who stopped or changed treatment

Question 18

What is the difference between statistical significance and clinical significance?

Answer 18

Statistical significance - difference in results is unlikely to be due to margin of error; it’s unlikely that the null hypothesis is true

Clinical significance - changing management will make a difference to patient outcomes, benefits outweigh risks e.g side effects

A study proving a drug lowers BP by 2 mmHg may be statistically significant but NOT clinically significant

Question 19

How do you calculate absolute risk?

Answer 19

Number of events observed / No. of participants in total

Question 20

How do you calculate relative risk?

Answer 20

Absolute risk _intervention / Absolute risk _control

Question 21

What is a confounding variable?

Answer 21

Variable which isn’t not being taken into account which may alter the results of a trial

Question 22

What is publication bias?

Answer 22

Trials which have valuable (but ‘boring’) results e.g proving the null hypothesis are less likely to be published in journals