5: Critical appraisal Flashcards
What is critical appraisal?
Evaluating a piece of research to determine if it’s valid i.e can you trust its methods and its conclusions
What is
a) internal
b) external
validity in relation to research?
a) Are the method and results sound
b) Can you apply the results of the study to real life
What does efficacy mean?
Ability to produce desired result
What does effectiveness mean?
Measure of an intervention’s benefit in real life
What is the impact factor of a journal?
How well respected it is, doesn’t automatically mean the study will be good but good journals tend not to accept crap studies
How does a cross-sectional study work?
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
Cross-sectional studies can only measure (incidence / prevalence).
prevalence
What is a case-control study?
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
Case-control and cross-sectional studies are (retrospective / prospective).
retrospective
What is a cohort study?
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
A cohort study is (prospective / retrospective).
prospective
In cohort studies, there is a risk that participants are ___ to follow-up.
lost
What is the gold-standard study design for clinical trials?
Randomised control trial
What does intention to treat mean in relation to randomised control trials?
Patient results are attributed to the group they were in initially, even if they change / stop the new intervention
What is per protocol analysis in relation to randomised control trials?
Only those who finish treatment on the new intervention are analysed in the ‘new intervention’ results
Whether you use intention to treat or per protocol analysis will change the study’s ___.
results
Which analysis method for RCTs (intention to treat or per protocol) is more accurate?
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
What is the difference between statistical significance and clinical significance?
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
How do you calculate absolute risk?
Number of events observed / No. of participants in total
How do you calculate relative risk?
Absolute risk intervention / Absolute risk control
What is a confounding variable?
Variable which isn’t not being taken into account which may alter the results of a trial
What is publication bias?
Trials which have valuable (but ‘boring’) results e.g proving the null hypothesis are less likely to be published in journals
