CriticaL Appraisal Of Specific Designs

Question 1

What is a case-control studies?

Answer 1

Selects cases and controls based on outcome, retrospective

Outcome measure is an odds ratio

Show associations not causal relationship

Question 2

Concerns in a case-control study

Answer 2

Selection bias

Recall bias

Misclassification bias - case is a control and control is a case e.g. not recorded correctly

Interviewer/ observer bias

Confounding

Question 3

What is a cohort study?

Answer 3

Select participants based on exposure status
Longitudinal prospective design
Outcome measure can be odds ratio, risk ratio, incidence rate ratio

Good for rare exposures

Question 4

Concerns with cohort study

Answer 4

Selection bias
Response bias 
Measurement bias
Healthy worker effect
Loss to follow up/ attrition bias
Confounding

Question 5

What do randomised controlled trails allow you to make?

Answer 5

Causal inferences - gold standard - eliminates confounding, blinding minimises bias not always possible

Question 6

Biggest concerns with randomised controlled trials

Answer 6

Confounding 
Bias
Loss to follow up 
Were data analyses in line with randomisation 
Measurements of outcome 
Actual blinding 
Actual randomisation 
Intention to treat

Question 7

What is a systematic review?

Answer 7

Bring together findings from several or many primary studies and provide accessible overview of these studies

May or may not include meta-analysis of data

Useful in decision making, help identify gaps and areas further research

Question 8

Concerns of systematic reviews

Answer 8

Completeness if search of evidence - grey literature
Assessment of quality and bias
Synthesis of data - similar enough studies
Precision of results
Publication bias - small studies