Classes 20-21 Case-Control Studies Flashcards Preview

Whitney - Epidemiology Test 2 > Classes 20-21 Case-Control Studies > Flashcards

Flashcards in Classes 20-21 Case-Control Studies Deck (24)
Loading flashcards...

Define Case-Control Studies

Observational, analytical studies allowing researcher to be passive observer of natural events occurring in individuals with the disease/condition of interest (cases) who are compared with people who do not have the condition of interest (controls)


In Case-control studies, group assignment is based on:

Disease Status


When are case-control studies useful?

When studying a rare disease or investigating an outbreak


Case-control studies commonly generate the _____ ______ as measure of association

Odds Ratio (OR)


Reasons to select a Case-Control design:

Unable to "randomize"
Limited resources
Disease of interest is rare
Prospective exposure date is difficult/expensive to obtain and/or very time inappopriate


Case-Control Studies are always:



Strengths of Case-Control Studies

Good for assessing multiple exposures of one outcome
Useful when diseases are rare
Useful in calculating odds or OR's
Less expensive
Useful when ethical issues limit Interventional studies
Useful in dynamic populations
Useful when disease has long induction/latent period


What does it mean for a study to be retrospective?

This means that the outcome is already known


Selection of cases in Case-control studies

Defined by the investigator using accurate, medically-reliable, and efficient data sources
Should be objective, consistent, and valid


Weaknesses of Case-control studies

Opposite of the strengths


Selection of controls in Case-control studies

Major determinant in whether any conclusion is valid (internal validity)
Make the groups as close as possible except the presence of the disease (control) of interest
Must be selected irrespective of exposure status


What is the goal in selecting controls in case-control studies?

To assess for the presence of an association between exposure & known condition of interest be selecting non-disease individuals from the sample population which produced the cases


True or False:
In a case-control study, it is possible for an individual to be both a case and a control in the same study

Can be associated with an outbreak investigation with multiple exposures OR in a situation of brief (acute) change in risk of the outcome in interest (hazard period) - "case-crossover" design


Describe a "case-crossover" design in case-control studies

Subjects are their own controls during the other times they don't have the acute change in risk
Only Case-Control study design able to adequately attempt to address issue of "temporality"


Nested Case-Control Studies

Case-Control Studies conducted after, or out of, a prospective Cohort study
Subjects in cohort study ultimately developing disease are defined as cases
Diseased used in a new (different) study design


Sampling types of controls used for nested case-control studies or when sampling is necessary from Cohort:

Survivor Sampling
Base Sampling
Risk-Set Sampling


Survivor Sampling

Sample of non-diseased individuals (survivors) at end off study period


Base Sampling

Sample of non-diseased individuals at start of study period


Risk-Set Sampling

Sample of non-diseased individuals during study period at same time when case was diagnosed


Selection Bias

Related to the way subjects are chosen for a study
Always a potential problem
Not too significant in Case-Crossover study designs


Recall Bias

Related to the amount/specificity that Cases or Controls recall past events DIFFERENTLY
Usually the Cases are more likely to recall


Individual Matching

Matches individuals based on specific patient-based characteristics
Used when each case has unique & important characteristics


Group Matching

Proportion of cases & proportion of controls with identical characteristics are matched
Requires cases be selected first


True or False:
You can match for anything, including possible risk factors.

Do NOT match for anything that might be a risk factor