Case Control Studies Flashcards
What type of study is a case control?
Observational retrospective- already know the outcome
What is the purpose of case control studies?
To observe natural events in individuals who have the disease compared to those without the disease or out come.
Useful for studying a rare disease or investigating an outbereak
How are groups allocated in a case control study?
Based upon disease status not forced or randomized
Why would you select a case control study design?
It is unethical to force someone to have cancer, you cant randomize or force allocate.
Limited resources time money or subjects.
The disease is reare and little is known it assesses the perspective of hypothesis
CONDUCTED RETROSPECTIVELY USUALLY
What are the pros to case control studies?
Can assess multiple exposures of one outcome
Useful for rare diseases
Useful in determining associations (not causation)
Less expensive than interventional
Useful when ethics can limit study
Useful for disease with long induction latent period
What are weaknesses to Case control studies?
Does NOT demonstrate causation.
Can be impacted by unaddressed confounders.
Retrospective- you can’t control for other exposure.
Impacted by biases- specifically recall.
Limited by data available.
What kind of statistics can be calculated from Case control studies?
Odds Ratio and odds of exposure
In a two by two table what is known at the start?
Column totals (A+C) and (B+D) –> disease presence yes or no
What are the primary biases worried about?
Selection and Recall
What do controls represent in a case control study?
Baseline risk of exposure in general population
In selecting controls what biases are a concern?
Selection and Internal Validity
How are controls selected?
Regardless of exposure status- try to be as equal as possible except for the disease
Where can controls come from?
- Population- state community neighborhood
- Institutional/organiztional/provider
- Spouse/relatives/friends
In determining whether there is an association between caffeine and risk of crashing in truck drivers who would be an acceptable control group?
Truck drivers who have not crashed- regardless of whether or not they drink caffeine.
What is the only case control design that can attempt to address temporality?
Case Crossover which looks at individuals who are their own controls during a time before they have a change . Day before a MI theyre a control day after they are now a case, you can see what changed.
