2.3 Case Control studies Flashcards
What type of study is Case control studies?
Observational studies
What do case control studies allow?
researcher to be a passive observer of natural events occurring in cases who are compared with controls
What are case control group assignments based on?
Disease status
What are case control studies useful for?
Rare disease or investigating an outbreak
What key word tells us that we are dealing with observational studies?
Randomly selected. Not randomized
What key word tells us that we are dealing with interventional studies?
Randomized
On the epi table, for case controls, what are we looking at?
A+C and B+D
What are 3 reasons to use a case control study?
Unable to force group allocation. Limited resources and disease is rare.
Case control studies are conducted in a what type of fashion?
Retrospective
What are the 5 strengths of case control studies?
- Good for multiple exposures of one outcome. 2 Usefull for rare diseases. 3 Determines associations (not causation). 4. Good with ethics. 5. Good when disease has a long induction/latent period.
What are 5 weaknesses of case control studies?
- Cant demonstrate causation. 2. confounders. 3. They are retrospective. 4. Have lots of bias. 5. Limited data due to retrospective nature.
How are the selection of cases for case control study designs?
want the most detailed criteria possible. So we hope these cases are accurate. Find out how did they find out they were cases. Missclaffication can be a problem. Still an error.
What is the recall counterfactual theory?
All else being equal except outcome. Requires exchangeablilty to other determinants of outcome
What is the most difficult part with case control studies?
Control selection
Why is the control selection the hardest?
The way the controls are selected is a major determinant in whether any conclusion is valid. Internal validity,, selection bias.
Where can control groups come from? 3 ways
Population, institutional/organization/provider, spouse/relatives/friends.
True or False? An individual can function as both an exposed and unexposed individual in the same study?
True
How can a pt be in both the exposed and unexposed group in the same study?
Via outbreak investigation with multiple exposures or case-crossover
What are Nested case control studies?
like case control, but nested and comes form another study. Developed as case study after another study.
What are three ways Nested case control studies sample from other studies?
Survivor, base and risk set sampling.
What is survivor sampling?
Sample of survivors at END of study period
What is base sampling?
Sample of non diseased individuals at START of study period
What is risk-set sampling?
Sample of non diseased individula DURING study period at same time when case was diagnosed.
What is selection bias?
To the way subjects are chosen for study
