Observ. Study Designs

Question 1

define association

Answer 1

a statistical measure of dependence/relationship between two events, characteristics, or variables

Question 2

define causation or causal inference

Answer 2

Observations made in a research study provide evidence for
making causal inferences

Question 3

what are Bradford Hill’s Criteria for Causation

Answer 3

strength of association
consistency
specificity
temporality
biologic agent
biologic plausibility
coherence
experimental evidence
analogy

Question 4

what are causes of causal inference?

Answer 4

true/causal effect
chance
confounding
effect modification
bias

Question 5

what is the hierarchy for causal inference? (most likely to have causal inference -> least likely) and outline the the variables that make the hierarchy not absoulte

Answer 5

Randomized clinical trial -> cohort -> case-control -> cross-sectional -> case series

A poorly documented cohort study may not provide as high of quality of knowledge than a well-designed case-control study, so quality of study is important

Question 6

what do risk measures quantify?

Answer 6

probability of a given outcome in groups of people

Question 7

as an example, we want to answer the question of: *Is Azithromycin use associated with increased risk of death due to cardiovascular causes?
we must first identify the exposure of interest and the outcome of interest. What would E,D,Ē,Ď be/what do they mean?

Answer 7

E= exposure -> person who has used azithromycin and did not experience CV death
D= disease/outcome -> Person who has used azithromycin and did experience CV death
Ē= without exposure -> Person who has not used azithromycin and did not experience CV death
Ď= without disease/outcome -> Person who has not used azithromycin and did experience CV death

Question 8

outline the method of a case series

Answer 8

studies “case” patients only (no control group) who have the disease or outcome of interest. also for patients who all took the same treatment and the study monitors the outcome

Question 9

T/F case series cannot measure association or causal inference

Answer 9

true

Question 10

what are the steps involved with conducting a cross-sectional study

Answer 10

1. identify population of interest
2. define point/period in time
3. identify who is exposed and who is disease
4. calculate burden of disease

Question 11

what is a main disadvantage of cross-sectional studies?

Answer 11

no time component: collects info for a single point or short duration of time

Question 12

what are the steps involved with conducting a case-control study?

Answer 12

1. Within the population of interest
2. Sample disease and non-diseased persons
3. Retrospectively identify exposure status

Question 13

what are the steps involved with conducting a cohort study?

Answer 13

1. Beginning with persons without disease,
   but at risk
2. Identify exposed and unexposed persons
3. Follow through time to observe incidence
   of disease
4. Measure association by comparing
   incidence in exposed and unexposed

Question 14

there are two types of cohort studies: prospective and retrospective. what are the differences?

Answer 14

prospective studies recruit patients in present time and “follow” the moving forward in time whereas retrospective starts in some point in the past and measure data using an existing database or registry

Question 15

what is prevalence and how do we calculate it?

Answer 15

a measure of the burden of disease
equals= # diseased during specified time / # in population during specified time

Question 16

what is incidence and how do we calculate it?

Answer 16

a measure of risk
#New persons with diseaseduring given time period / Total # at risk persons during given time period

Question 17

*review slide 12-18 of Measures of Burden, Risk, and Association

Question 18

*REVIEW SLIDE 22 TO CALCULATE RELATIVE RISK AND RISK DIFFERENCE

Question 19

how do we interpret the value we get for relative risk?

Answer 19

RR > 1: E is a risk factor for D
RR = 1: E is not associated with D
RR < 1: E is protective of D

Question 20

how do we interpret the value we get for risk difference?

Answer 20

RD > 0: E is risk factor for D
RD = 0: E is not associated with D
RD < 0: E is protective of D

Question 21

both odds and risk can be identified for in which study design?

Answer 21

cohort studies

Question 22

what are the methods used for a cohort study?

Answer 22

aims to sample a group of people who share a defining characteristic (such as smoking) through a period of time to determine if the similar exposure (smoking) has any correlation to the disease (lung cancer)

Question 23

what are methods used for a case series study?
what form of bias are they selectively prone to and why?

Answer 23

study that tracks multiple subjects with a known exposure, such as patients who have received a similar treatment, or examines their medical records for exposure and outcome.
they are vulnerable to selection bias because they often use subjects from isolated environments (such as the hospital)

Question 24

what are methods used for a case-control study?

Answer 24

study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). used to determine causality

Question 25

what are the methods used for a cross-sectional study?
what form of bias are they selectively prone to?

Answer 25

a type of research design in which you collect data from many different individuals at a single point in time.
recall bias