STUDY DESIGN Flashcards
What is a case?
Someone who has the disease or event of interest
What is a control?
Someone who does not have the disease or event of interest
What is an exposure?
A factor which changes the likelihood that a person will develop a disease (e.g. infectious agent or toxin)
What is an outcome?
The outcome of the study, often the development of a specific disease
What are different study designs used for?
To examine the relationship between the “exposure” and “outcome”
In case control studies, what are cases and control selection based upon?
Cases should represent cases in a specified population group
- Controls are people without the disease
In case control studies, how is the exposure determined?
Medical records and patient interview
What do we measure in case control studies?
The odds ratio (odds of exposure)
What is one example of when you use case control studies?
For risk factors and risk identification
In cohort studies, what does a cohort need to be ?
Accessible
- Outcome free prior to exposure
- Needs to be some within group who will potentially be exposed and thus may present with the outcome
- Needs to be some within the group who don’t present with the outcome
What do cohort studies NOT have to include in cohort?
People of a PARTICULAR POPULATION
In a cohort study, what factors does the length of the follow up depend on?
- objectives of the study
- Outcomes being assessed
- the longer they go for, the potential for more information but have the problem of loss to follow up
What are the advantages of a cohort study (4)?
- Identify the natural history of the disorder
- Identify the temporal sequence between cause and outcome
- Good for rare exposures and common outcomes
- Very rigorous epidemiological design
What are the limitations of a cohort study
(5)?
Selection bias
- Exposed and non exposed subjects differ on important predictions of outcome
- Insufficient to study rare diseases
- Loss to follow up (exposure status)
- Expensive and time consuming
What is the most efficient study design to explore the cause of a rare disease?
A case control study
What is the most efficient study design to explore the cause of a rare exposure?
Cohort study (follow up)
What word do you look for when identifying cohort study?
Follow up
What are examples of analytical studies?
Case control, cohort, cross sectional study designs
Can an odds ratio of exposure be computed in a case control study?
YES! To estimate the strength of association between the source and disease.
What is a case control study good for?
- A clearly defined SINGLE outcome, RARE DISEASE
- Good if there is large popualtion at risk
- Multiple exposures to be examined
What are the problems with a case control study?
- Choice of appropriate controls
- Recall bias for cases (incentive to remember)
Can a cohort study allow for relative risk to be calculated ?
YES!
- Risk (attack) rates for exposed and unexposed (various exposures if necessary) used to compute relative risks of getting disease in exposed versus unexposed
