Unit 4: Observational Study Design (Part 2)

Question 1

in ____ studies, study subjects are grouped into one of two categories:
- Cases: disease/outcome positive (O+);
- Controls: disease/outcome negative (O-).
Investigators then look backwards in time to assess whether each subject was exposed (E+) or not (E-) to a given set of exposures of interest.

Answer 1

case-control

Question 2

Can the prevalence be estimated from the data obtained only from a case-control study

Answer 2

no

Question 3

this type of study is is useful as a first step when searching for a cause of an adverse health outcome

Answer 3

case-control

Question 4

Out of the three main forms of observational studies, these types of studies are the most prone to bias

Answer 4

case-control

Question 5

a ____ is a clear and explicit set of criteria that minimize the likelihood of a true case being missed and of a non-affected person being falsely classified as a case

Answer 5

case definition

Question 6

A population from which the cases that arise can be easily defined is called a ____ in a case-control study

Answer 6

primary study base

Question 7

A population/group of potential study subjects that is one or more steps removed from the primary population is called the ____ in a case-control study

Answer 7

secondary study base

Question 8

The two criteria to go through when selecting controls from a secondary study base are:

Answer 8

• Randomly select controls from the non-cases in the list/population the cases were chosen from
• The controls selected in the first step should be selected from diagnostic categories not associated with the exposure(s) of interest.

Question 9

Can you calculate relative risks from case-control studies?

Answer 9

No. these studies don’t calculate incidence of disease and by definition, relative risk is the ratio of the incidence in the exposed and non-exposed groups.

Question 10

What is used to estimate the relative risk in case-control studies?

Answer 10

Odds ratio

Question 11

in ____ studies study subjects are each grouped into one of two categories: Exposed (E+) and Not Exposed (E-). Investigators then follow these groups over a pre-determined time period to estimate incidence of disease in each exposure group

Answer 11

cohort

Question 12

What is important about the disease status of all subjects at the beginning of a cohort study?

Answer 12

all subjects must be disease-free

Question 13

during a ____ cohort study, exposure and unexposure are ascertained as they occur during the study; the groups are then followed for several years into the future and incidence is measured.

Answer 13

prospective cohort

Question 14

In a ____ cohort study, exposure is ascertained from past records and the outcome (development or no development of disease) is determined when the study is begun.

Answer 14

retrospective

Question 15

In ____ studies, the controls are a sample of individuals who are at risk for the disease at the time each case of the disease develops

Answer 15

nested case-control

Question 16

In a ____ study, cases develop at the same times that were seen in the nested case-control design, but the controls are randomly chosen from the defined cohort with which the study began

Answer 16

case-cohort

Question 17

Can you calculate the relative risk from the data a cohort study provides?

Answer 17

Yes. cohort studies measure incidence of disease (new cases)

Question 18

Which of the three studies are good for studying multiple exposure and outcome hypotheses?

Answer 18

cross-sectional

Question 19

Which of the three studies are good for studying rare outcomes?

Answer 19

Case-control

Question 20

Which of the three studies are good for studying rare exposures?

Answer 20

cohort