Module 8 (Ch.9) Flashcards
In a case-control study, people with a health outcome (disease) are compared to those without the health outcome (disease). ________ are people who have disease. ________ are people who don’t have disease.
In a case-control study, people with a health outcome (disease) are compared to those without the health outcome (disease). Cases are people who have disease. Controls are people who don’t have disease.
A case-control study allows you to relate exposure to a disease
Why do some people criticize case-control studies?
They say that the logic (looking at an effect to find a cause) seems backwards and that these studies seem more prone to bias than other designs
Which of the following is not a reason to choose a case-control study design:
* Don’t have exposure data
* Don’t have time in your schedule to do a randomized trial
* Disease of interest is rare
* Disease has long induction and latent period
* Little is known about the disease
* Underlying population is dynamic
Don’t have time in your schedule to do a randomized trial is not a reason to do a case-control study. The others in the list are good reasons for a case-control study.
It is best to use all available evidence to define with as much accuracy as possible the true cases of disease. True or False?
True
if________ criteria is used for cases, most cases will be captured (but not all) and many people who do not have the disease will be misclassified.
if nonspecific criteria is used for cases, most cases will be captured (but not all) and many people who do not have the disease will be misclassified.
If ________ of a criteria for cases is used, fewer cases will be captured and the sample size will be smaller.
If too restrictive of a criteria for cases is used, fewer cases will be captured and the sample size will be smaller.
what are good sources for identifying cases of disease?
- hospital or clinic patient rosters
- death certificates
- special reporting systems
- cancer registries
- birth defect registries
Researchers who study the causes of disease are most interested in the ____________ (incident or prevalent) cases because they are interested in the factors that lead to developing the disease.
Researchers who study the causes of disease are most interested in the incident cases because they are interested in the factors that lead to developing the disease.
________ are a sample of the source population
that gave rise to the cases
Controls are a sample of the source population
that gave rise to the cases
Cases and controls should represent the same
________ population
Cases and controls should represent the same
source population
Should exposure status play a role in who is
chosen as a control?
No, exposure status shouldn’t determine who is chosen as control
What is the “the would criterion” in a case-control study design?
the “would criterion” says if a member of the control group actually had the health condition under
study, they should end up as a case in your study.
Control groups are often selected from a hospital population (when cases are selected from a hospital population) and controls are selected from ____________ (when the cases are from a defined geographic location).
Control groups are often selected from a hospital population (when cases are selected from a hospital population) and controls are selected from the general population (when the cases are from a defined geographic location).
What are advantages and disadvantages to using hospital patients as controls?
Advantages
* Easy access
* Less bias
Disadvantages
* Their own illness (it can be okay if the illness has no relation to the risk factors under study
* It can be difficult to make sure that you only choose controls that have the same referral pattern as the cases (acute condition vs acute condition, chronic vs chronic)
What are advantages and disadvantages to using people from the general population as controls?
Advantage
* Selected from same population as cases
Disadvantages
* Time consuming
* expensive
* May remember exposures differently than cases (recall bias)
How do you recruit non-hospitalized controls?
- Door-to-door recruiting
- Telephone recruiting
- Other sources
- School enrollment lists
- Insurance company lists
- Selective service registry
Matching controls to cases helps to ensure similarity in the two groups, which should be similar except for ____________.
Matching controls to cases helps to ensure similarity in the two groups, which should be similar except for ____________.
Matching controls to cases helps to ensure similarity in the two groups
____________ controls to cases helps to ensure similarity in the two groups
( Group matching or individual matching ) is when you select cases and then match controls to match proportions.
Group matching is when you select cases and then match controls to match proportions.
(Group matching or individual matching) is when you individually match each control to a case creating matched pairs
Individual matching is when you individually match each control to a case creating matched pairs
What are some problems with matching?
- Trying to match by too many
- If you match by a characteristic, then you can’t study that characteristic
What is recall bias?
Some people may have better memories of
certain events than others
* Cases may have spent time thinking of their
own potential exposures and may recall these
more than a control
what measure of association is used for case-control studies?
Odds ratio - which tells us the odds of having a positive exposure history
The definition of odds is the ratio of the probability of
an event occurring to that of it not occurring. True or False?
True
What is the formula for the odds ratio?
OR = Odds that an exposed person is a case / Odds that an unexposed person is a case
OR = ad/bc , OR = a/b divided by c/d
Interpreting odds ratio
- What does it mean if an OR is equal to 1?
- What does it mean if an OR is greater than 1?
- What does it mean if an OR is less than?
- OR = 1: There is no evidence of an association between exposure and health outcome
- OR > 1: There is a positive association between exposure and a health outcome (it may
be causal) - OR < 1: There is a negative association between exposure and health outcome(The
exposure may be protective)
What are some strength of case-control studies?
- Efficient for rare diseases and diseases with long induction and latent period
- Can evaluate many risk factors for the same disease
What are some weaknesses of case-control studies?
- Inefficient for rare exposures
- Vulnerable to bias because of retrospective nature of study
- May have poor information on exposure because retrospective
- Difficult to infer temporal relationship between exposure and disease
Compare case-control studies to cohort studies
Cohort studies compare people with exposure to people
without exposure. Case-control studies compare people with disease to people without disease.
What are cross sectional studies?
- Exposure and health outcome outcome are
identified simultaneously for a study subject - Snapshot of the population
What are ecological studies?
These are studies of the characteristics of
groups
