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RUSVM Epidemiology 2016 > Study Designs > Flashcards

Flashcards in Study Designs Deck (36):
1

Descriptive Studies

describe disease:
Characteristics, amount, and distribution of disease

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Analytical Studies

Identify associations: Determine if there is an association between an exposure and outcome in a population and how strong the association is
The ultimate goal is to determine if an exposure factor causes the disease

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Characteristics of a good study

Scientifically sound
Valid
Precise
Efficient

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What are the different types of descriptive study designs?

Case Reports
Case Series
Cross-sectional descriptive studies

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What is an analytical experimental study design?

Clinical trials

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What is an analytical observational study design that compares groups of populations?

Ecological

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What is an analytical observational study design that compares groups of Individuals?

Cross-sectional analytical studies
Case-control
Cohort (prospective and retrospective)

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Hypothesis

a statement about an association between an exposure and an outcome

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One study subject in a descriptive study design

Case Report

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A Few study subjects in a descriptive study design

Case Series

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What are the advantages of Case Reports and Case Series?

Require minimal resources
relatively quick to perform
Provide information to stimulate hypotheses and future analytical studies

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What are the disadvantages of Case Reports & Case Series?

Small number of cases
Findings may be atypical or aberrant
Strictly descriptive
Findings are not generalizable to the population

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A descriptive study design with Lots of study subjects

Cross-sectional study

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Cross-sectional study

Sample of the population
Estimate the amount and distribution of disease
Measure of disease occurrence is usually prevalence

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What are the steps of a cross-sectional study?

1. Select subjects from the source population
2. Measure the disease in each study subject
3. Calculate the measure of disease occurrence

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What are the advantages of a cross-sectional study

Can generalize to the population
Fast and Cheap
Provide good descriptive or baseline for future studies

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What are the disadvantages of a cross-sectional study

Not good for causality
Prevalence is of limited value

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What are the two types of Analytical studies?

Experimental
Observational

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Association

when the exposure if dependent on the outcome

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Allocated

Assigned

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Blinding

researcher doesn't know the treatment or exposure status of subjects

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Random Selection

Randomly select study subjects for inclusion

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Random Allocation

Randomly allocated subjects to exposure groups

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What are the advantages of Experimental studies?

Establish causality
Free of bias and confounding
Statistically powerful
Exposures and outcomes are clearly measured during the study - no recall bias

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Disadvantages of Experimental studies?

Expensive
Very narrow in scope
Not always ethical to randomly allocate treatment
"Placebo effect"
Loss of follow up can be higher for some treatments

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Case control studies

Individual Subjects are selected to represent outcome groups
Subjects are selected because of their outcome status

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What are the advantages of Case-control studies?

Short timeline
Can look at multiple risk factors at one time
Good for studying rare diseases

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What are the disadvantages of Case-control studies?

Poor selection of controls can invalidate the entire study
Recall bias
Incomplete clinical records

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Cohort Studies

Individual subjects are selected to represent exposure groups

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What are the two types of Cohort Studies?

Prospective cohort studies
Retrospective Cohort Studies

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Prospective cohort study

Forward in time

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Retrospective cohort study

Back in time
Subjects are selected based on their exposure status, then their outcome status is determined from their history, by reviewing records, questionnaires, testing them to determine if they have the outcome

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Advantages of Prospective cohort studies

Establish Causality
Multiple exposures at one time
study of rare exposures

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Disadvantages of Prospective Cohort Studies

Take a long time
deal with changing study populations
Depends upon accurate assessment of exposures and consistent assessment of outcomes over time

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Advantages of Retrospective Cohort studies

Short timeline - disease has already occurred
look at multiple exposures at one time
studying rare exposures

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Disadvantages of Retrospective Cohort Studies

Not good for establishing causality
Poor selection of controls can invalidate the entire study
Depends upon accurate assessment of diseases that happened in the past
Recall bias
Incomplete clinical records