REBM Flashcards
What you call a study with this structure?
Case control study
In a case control study what do you call the group of people whos outcome is the outcome in question?
Cases
What is a downside to a case control study?
Exposure is historical hence patients often under or over estimate their exposure
What is a case control study best used for?
Prognosis questions?
What would you call a study with this structure?
Cohort study
When are cohort studies useful?
- If there is already a strong hypothesis linking exposure to outcome
- The time between exposure and outcome is not too long
- The outcome is not too rare
How does a randomised controlled trial differ from a cohort study?
They are the best when looking at the effectiveness of a specific intervention, they are also free from selection bias.
However they can be costly and have ethical issues
What would you call a study witht his structure?
Cross-Sectional Study
What are cross sectional studies useful for?
- Answering question of incidence or prevelence within a population
- Establishing what is the norm for specific populations at moments in time
- To justify further research on a topic, they can indicate relationships but are rarely strong evidence by themselves
What would you can a study with this structure?
Case study
What are case studies good for?
- Can provide extensive details on abnoramal outcomes and rare conditions
Pitfalls of a case study
- Hard to replicate
- Hard to rule out other contributing factors
What is relative risk (RR)?
Incidence in Exposed / Incidence in Unexposed
Odds Ratio (OR)
Odds Ratio (OR) = Odds of outcome in Exposed / Odds of outcome in Unexposed
What is Odds?
Odds = ( # cases ) / ( # non-cases )
What Bias would this be an example of?
Subjects in study different to subjects not in studye.g. volunteers, cases referred from specialist clinics
Selection bias
What bias would this be an example of?
Different processing for case & control samples Different interviewers
Measurement Bias
What bias is this an example of?
Cases remember exposures better than controls? Cases exaggerate exposures more than controls
Recall bias
What is the word for when factors may mask an actual association or, more commonly, falsely demonstrate an apparent association between the treatment and outcome when no real association between them exists.
Confounding factors
