Epidemiology Week 13

Question 1

Necessary

Answer 1

Without the factor, disease never develops

Question 2

Sufficient

Answer 2

In presence of the factor, disease always develops

Question 3

Necessary & Sufficient

Answer 3

Disease always develops in presence of the factor, but never without it. Least likely; rarely if ever happens.

Question 4

Necessary but not sufficient

Answer 4

The factor is necessary to cause the disease, but other factors are required as well. Disease will not always occur just because factor is present.

Question 5

Sufficient but not necessary

Answer 5

The factor alone can produce the disease, but it is not the only thing that can cause it; other factors also can.

Question 6

Neither necessary nor sufficient

Answer 6

No one factor working alone can cause disease, & many combinations possible. Most likely.

Question 7

Guidelines for proof of casaul relationship

Answer 7

1) Temporal relationship
2) Strength of association
3) Dose-response relationship
4) Replication of the findings
5) Biologic plausibility
6) Consideration of alternate explanations
7) Cessation of exposure
8) Consistency with other knowledge
9) Specificity of the association

Question 8

Temporal relationship

Answer 8

Factor occurred before the disease onset.

Easier to establish in prospective cohort than case-control or retrospective

Question 9

Strength of association

Answer 9

Relative risk or odds ratio. The stronger, the more likely to be causal.

Question 10

Dose-response relationship

Answer 10

As dose of exposure increases, so does risk of disease

Question 11

Replication of findings

Answer 11

Consistent between subgroups, between studies, between populations

Question 12

Biologic plausibility

Answer 12

Coherence with current body of biologic knowledge. Some examples where clinical findings have preceded biologic knowledge.

Question 13

Consideration of alternate explanations

Answer 13

Potential confounders have been accounted for & ruled out

Question 14

Cessation of exposure

Answer 14

Risk decreases as exposure decreases

Question 15

Consistency with other knowledge

Answer 15

Findings consistent with other data (such as lung cancer rates & cigarette sales)

Question 16

Specificity of the association

Answer 16

When one disease is associated with one factor. Weakest of all guidelines.

Question 17

Selection bias

Answer 17

The way in which cases & controls are selected is not random

Question 18

Exclusion bias

Answer 18

Results from applying different criteria to cases & controls in regard to inclusion in the study

Question 19

Information bias

Answer 19

Way of gathering information among subjects is inadequate, so some of the information is incorrect

Question 20

Misclassification bias

Answer 20

Some cases are classified as controls or vice versa

Question 21

Differential misclassification

Answer 21

Rates of misclassification are different for control vs case groups

Question 22

Non-differential misclassification

Answer 22

Results from data collection methods

Question 23

Surveillance bias

Answer 23

Disease ascertainment better in the monitored population than in general population

Question 24

Recall bias

Answer 24

Potential exposure recalled by cases, forgotten by controls

Question 25

Wish bias

Answer 25

Under-reporting of exposures related to lifestyle, overemphasis of exposures related to work or environment

Question 26

Confounder

Answer 26

In a study of whether factor A causes disease B, factor X is a confounder if

1) Factor X is a known risk factor for disease B
2) Factor X is associated with factor A, but is not a result of factor A

Question 27

True or false: a confounder is an error in the study.

Answer 27

False. It is a valid finding that must be taken into account in the study of the disease.

Question 28

Interaction

Answer 28

When the incidence rate in the presence of 2 factors differs from the incidence rate we would expect to find from their individual effects