case-control studies

Question 1

cases

case-control studies

Answer 1

have disease of interest

Question 2

controls

case-control studies

Answer 2

don’t have disease of interest but COULD develop it

Question 3

pros

case-control studies

Answer 3

• cheap bc smaller sample size
• good for diseases where medical care is sought
• provides leads for follow-up
• good for disease with long-lattency (takes long time to develop, we don’t have to wait bc it is retrospective)
• rare disease
• multiple exposures
• FAST
• good for rapid onset disease (can sort out what caused vs what is result of something)

Question 4

cons

case-control studies

Answer 4

• retrospective –> biase
• need records
• can’t establish, risk, prevalence, incidence
• can only study 1 disease
• can’t determine cause and effect
• info on confounders may not be available
• cases may search for cause of their disease and over-report exposure
• assembling casees may be hard
• identifying control might be hard

Question 5

when do we use case-control studies

Answer 5

to examine a possible relationship btwn exposure and disease

Question 6

start with

case-control studies

Answer 6

cases and controls, then measure exposure

Question 7

odds ratio =

case-control studies

Answer 7

ad/bc

Question 8

OR = 1.2

Answer 8

the odds of using artifical sweeteners is 1.02 times greater in bladder cancer cases than in controls

Question 9

if exposure is associated with disease, we expect

Answer 9

more exposed in cases than controls

Question 10

OR < 1

case-control studies

Answer 10

protective factor

Question 11

OR = 1

case-control studies

Answer 11

no association

Question 12

OR = 2

case-control studies

Answer 12

cases twice as likely as controls

Question 13

95% confidence interbal

case-control studies

Answer 13

if 1 is included, OR is not significant
if 1 is NOT included, OR is significant

Question 14

OR provides good estimate of risk when

case-control studies

Answer 14

1. controls are representative of target population
2. cases are representative of all cases
3. frequency of disease in population is small, disease is rare

Question 15

design: finding cases

case-control studies

Answer 15

• define case conceptually and enroll in a specific time period
• tumor registry or vital statistics registry
• medical facilities
• hospital cases (multicenter is best)
• doctor’s office
• community patient registry

Question 16

sources of controls

case-control studies

Answer 16

non hospitalized controls:
* community: can be probability sample
* neighborhood controls
* random digit dialing to match neighborhood
* friend control
hospitalized controls:
* all other patients
* defined diagnosis

Question 17

exposure

case-control studies

Answer 17

• exposure must be designed same in case and control
• if looking through records, don’t let researcher know hypothesis
• assure no routine recording of variable of interest in records
• avoid physical measures that may be influenced by diseased state

Question 18

wording of questions

Answer 18

• need to be sure exposure preceded disease
• diet and colon cancer: ask about diet before symptoms
• overian cancer and weight: ask about weight several years before diagnosis
• may need to exclude ppl w/ symptoms >1 yr ago

Question 19

recall of exposure limitations

case-control studies

Answer 19

1. limitations in recall
2. recall bias

Question 20

limitations in recal

case-control studies

Answer 20

ppl might not know specific info or remember

Question 21

recall bias

case-control studies

Answer 21

cases may recall info to ggreater extent than controls
differential recall may lead to artifactual relationship

Question 22

use of multiple controls

case-control studies

Answer 22

2 or 3 same controls per case increases power of study
controls of diff types may help (if looking at risk for brain tumors have a normal control and other cancer control)

Question 23

nested case control study

case-control studies

Answer 23

case control nested in cohort study
population in defined cohort with baseline surveys and samples followed over time
cases: those who develop disease over time

Question 24

advantages of nested case control

Answer 24

data collected before disease develops (no recall bias)
cheaper than analyzing all samples for all cohort members

Question 25

nested case control start with

Answer 25

defined cohort
overtime, categorize into develop disease (cases) and have not developed (controls)

Question 26

what is coffee drinking incases is greater than that in controls?

Answer 26

this is a diff in exposure
matching will fix

Question 27

matching

Answer 27

match controls and cases for confounders (age, sex, race, SES, job)

Question 28

group matching

Answer 28

select controls so proprtion of controls have same characteristic as a proportion of cases

Question 29

individual matching

Answer 29

for each selected case, a control is selected who is similar to the case in terms of the matching variables

Question 30

concordant pairs

Answer 30

pairs in which both case and control are exposed
OR
neither exposed

Question 31

discordant pairs

Answer 31

case exposed, control not
OR
control exposed, case not

Question 32

analysis of case-control

Answer 32

logistical regression analysis