Lecture 2 - Clinical Questions and Study Types Flashcards
What is the hierarchy of evidence (for intervention questions primarily)?
- Systematic Reviews and Meta-analyses
- RCT
- Pseudo-randomized controlled trial
- Cohort Studies (comparative)
- Case Control Studies (comparative)
- Case Series
- Case Reports
- Expert opinion, editorials, ideas
- Animal research
- In vitro (test tube) research
What is the study design hierarchy?
- RCT (only one that is experimental)
- Cohort Study
- Case Control Study
- Cross sectional study / clinical observational
For diagnostic purposes, which study type is preferred?
Cross sectional with reference standard
For therapeutic purposes, which study type is preferred?
RCT
For prognostic purposes, which study type is preferred?
Inception cohort
For risk factor/etiology purposes, which study type is preferred?
RCT (but it’s often not ethical or feasible) so Cohort or Case control study
For prevalence/frequency purposes, which study type is preferred?
Random Sample / Cross sectional
What are some key points of Case series?
- Raise awareness of an important issue
- Learning example
- New diseases or treatment
What are some key points of Cross-sectional studies?
- Observational studies
- Insights into diseases and associations (example is smoking and lung cancer)
Which studies have control groups?
- Case control study
- Cohort studies
- RCT
How are case control studies organized?
Cases with disease or ‘outcome’ enrolled, then control group of similar patients without disease collected
(you look back in time to see what the patient was exposed to and not exposed to)
How are cohort studies organized?
Subgroups within the cohort become ‘control’ or comparison groups (eg smokers vs non-smokers compared to see if a particular outcome different these groups. May be multiple comparison groups in one cohort)
*Direction of inquiry is looking forward not looking back like case control studies
How are RCT studies organized?
Study participants selected, then randomized into intervention or control group
What are some strengths of case control study?
- Good for rare disease or disease with long lead times
- Less expensive
- Smaller participants needed than cohort or RCT
What are some weaknesses of case control study?
- Less accurate and less able to inform cause than cohort and RCT
- Controls not similar enough to cases
- Recall bias exists (people with disease may be more likely to remember past exposures than those without disease)
- Confounding (try to control with stratification and statistical adjustment)
