Chapter 10 (from in class packet)

Question 0

What are the 2 measures of association?

Answer 0

risk and odds

Question 1

what are the 4 steps to case-control studies?

Answer 1

1. select 2 groups of people with disease and without disease
2. ascertain the exposure
3. determine the PROPORTION of EXPOSED among the cases and the PROPORTION OF NONEXPOSED among the cases. the same with controls
4. the proportion of cases who were exposed is compared with the proportion of controls who were exposed

Question 2

what is the formula for risks (measures of association)

Answer 2

chances of something happening/ chances of ALL things happening

Question 3

what is the formula for odds (measures of association)?

Answer 3

chances of something happening/ chances of NOT happening

Question 4

what is the probability that the event does not occur? (equation)

Answer 4

1-p

Question 5

what is the odds of the event equation?

Answer 5

O= p/1-p

Question 6

what is the odds ratio?

Answer 6

the odds of exposure among the cases/the odds of exposure among the controls

Question 7

what is the MEASURE of ASSOCIATION between disease and exposure in a case-control study?

Answer 7

OR= ad/bc

Question 8

what is the odd EXPOSURE in the cases is EQUAL to the odds of exposure in the controls (no association)

Answer 8

OR=1

Question 9

what is the odds of EXPOSURE in the cases is GREATER than the odds of exposure in the controls (positive association)?

Answer 9

OR>1

Question 10

what is the odds of EXPOSURE in the cases in LESS than the odds of exposure in the controls (negative association)? protective effect

Answer 10

OR<1

Question 11

when the disease IS RARE what happens?

Answer 11

OR~RR

Question 12

When the disease is NOT RARE what happens?

Answer 12

OR>RR

Question 13

what is the process of selecting the controls so that they are similar to the cases?

Answer 13

matching

Question 14

if you match too many characteristics then what happens?

Answer 14

it will be difficult to identify an appropriate control

Question 15

if you match on a given characteristic can you use this characteristic again?

Answer 15

NO

Question 16

which OR do you use during a matched case-control study?

Answer 16

b/c

Question 17

What are the 4 steps when doing a CASE selection?

Answer 17

1. establish a case definition
2. cases can be new cases or existing case
3. cases must be representative of persons with disease
4. sources: hospitals, ph clinics, physician offices, HMOs, diseases registries

Question 18

What are the 4 steps when doing a CONTROL selection?

Answer 18

1. controls are subjects free of disease
2. controls should come from the same source of population as the case
3. the prevalence of exposure of the controls should be similar with the prevalence of exposure among the source of population
4. sources: general population, random digit dialing, friends/relatives, hospital or clinic based

Question 19

how many controls per case?

Answer 19

1:1

Question 20

How can the number of case be increased?

Answer 20

by using more than one control case

Question 21

what are the 2 parts of assess exposure?

Answer 21

• study subjects

- existing records

Question 22

what are study subjects?

Answer 22

self-reported questionnaire

- particularly vulnerable to recall bias as cases may recall their exposure history more thoroughly than controls

Question 23

What is existing records?

Answer 23

• work histories (industrial hygiene)
• hospital (birth, diagnostic, x-ray)
• prescriptions

Question 24

List case-control study advantages.

Answer 24

• quick and expensive
• small sample sizes
• optimal for evaluation of rare diseases
• can examine multiple etiologic factors for a single disease

Question 25

List case-control study disadvantages

Answer 25

• inefficient evaluation of rare exposures unless the disease is common among the exposed
• disease status can influence the selection of case and control subjects
• may be difficult to establish the temporal relationship between exposure and disease. exposure measurements are collected after disease occurence
• prone to bias compared to analytic designs, in particular, selection and recall bias

Question 26

When does nested case-control study occur?

Answer 26

• after the establishment of a cohort study

Question 27

List some advantages of a nested case-control study

Answer 27

• decrease in recall bias
• identify risk factors, rather than early or subclinical disease as the specimens were obtained years before disease occurs
• less expensive
• increased comparability