Study Designs

Question 1

Descriptive Studies

Answer 1

describe disease:

Characteristics, amount, and distribution of disease

Question 2

Analytical Studies

Answer 2

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

Question 3

Characteristics of a good study

Answer 3

Scientifically sound
Valid
Precise
Efficient

Question 4

What are the different types of descriptive study designs?

Answer 4

Case Reports
Case Series
Cross-sectional descriptive studies

Question 5

What is an analytical experimental study design?

Answer 5

Clinical trials

Question 6

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

Answer 6

Ecological

Question 7

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

Answer 7

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

Question 8

Hypothesis

Answer 8

a statement about an association between an exposure and an outcome

Question 9

One study subject in a descriptive study design

Answer 9

Case Report

Question 10

A Few study subjects in a descriptive study design

Answer 10

Case Series

Question 11

What are the advantages of Case Reports and Case Series?

Answer 11

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

Question 12

What are the disadvantages of Case Reports & Case Series?

Answer 12

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

Question 13

A descriptive study design with Lots of study subjects

Answer 13

Cross-sectional study

Question 14

Cross-sectional study

Answer 14

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

Question 15

What are the steps of a cross-sectional study?

Answer 15

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

Question 16

What are the advantages of a cross-sectional study

Answer 16

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

Question 17

What are the disadvantages of a cross-sectional study

Answer 17

Not good for causality

Prevalence is of limited value

Question 18

What are the two types of Analytical studies?

Answer 18

Experimental

Observational

Question 19

Association

Answer 19

when the exposure if dependent on the outcome

Question 20

Allocated

Answer 20

Assigned

Question 21

Blinding

Answer 21

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

Question 22

Random Selection

Answer 22

Randomly select study subjects for inclusion

Question 23

Random Allocation

Answer 23

Randomly allocated subjects to exposure groups

Question 24

What are the advantages of Experimental studies?

Answer 24

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

Question 25

Disadvantages of Experimental studies?

Answer 25

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

Question 26

Case control studies

Answer 26

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

Question 27

What are the advantages of Case-control studies?

Answer 27

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

Question 28

What are the disadvantages of Case-control studies?

Answer 28

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

Question 29

Cohort Studies

Answer 29

Individual subjects are selected to represent exposure groups

Question 30

What are the two types of Cohort Studies?

Answer 30

Prospective cohort studies | Retrospective Cohort Studies

Question 31

Prospective cohort study

Answer 31

Forward in time

Question 32

Retrospective cohort study

Answer 32

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

Question 33

Advantages of Prospective cohort studies

Answer 33

Establish Causality Multiple exposures at one time study of rare exposures

Question 34

Disadvantages of Prospective Cohort Studies

Answer 34

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

Question 35

Advantages of Retrospective Cohort studies

Answer 35

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

Question 36

Disadvantages of Retrospective Cohort Studies

Answer 36

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