Interpreting Epidemiological Findings (1)

Question 1

What are the Bradford hill criteria?

Answer 1

Strength
Consistency
Specificity
Temporality
Biological Gradient
Plausibility
Coherence
Experiment
Analogy

Question 2

What does strength mean?

Answer 2

A stronger association increases the confidence that an exposure causes an outcome

Question 3

What does consistency mean?

Answer 3

Consistent findings across settings tends to rule of errors or fallacies that might befall between studies

Question 4

What does specificity mean?

Answer 4

Specificity can be informative when present but its absence convey very little

Question 5

What is temporality?

Answer 5

Measuring over time

Question 6

What is biological gradient?

Answer 6

A dose-response effect is a compelling argument for causality

e.g. consuming more cigarettes increases likelihood of disease

Question 7

What is plausibility?

Answer 7

Relationship should be biologically plausible where the science is understood

Question 8

What is coherence?

Answer 8

The association ought to be consistent with the existing theory and knowledge

Question 9

What is experiment?

Answer 9

Evidence from experimentation should be supportive of the proposed link

Question 10

What is analogy?

Answer 10

Drawing upon analogous findings, we many make inference on the relationship

e.g. rubella causes deafness so you could consider that other viruses can cause similar issues

Question 11

What is bias?

Answer 11

Any trends in the collection, analysis, interpretation, publication or review of data that can lead to conclusions that are systematically different from the truth

Question 12

What are the three types of bias?

Answer 12

Selection
Information
Compounding

Question 13

What is internal validity?

Answer 13

The extent to which findings accurately describe the relationship between exposure and outcome in the context of the study

Question 14

What is external validity?

Answer 14

Generalisiability

Question 15

What can selection bias also be called?

What is selection bias?

How can you avoid selection bias?

Answer 15

Berkson’s bias (in hospitals)
Healthy worker effect (occupational studies)

Occurs when individuals or groups in a study differ systematically from target population leading to a systematic error in an association or outcome

Controls representative of target population
Minimise non-response (i.e declining to participate)
Compare respondents with non respondents

Question 16

What is information bias?

Answer 16

Due to a number reasons we have misclassification of the exposure or disease status (or both)

Can include: interviewer, recall, response, and diagnostic bias

Question 17

What is interviewer bias?

Answer 17

Interviewers ask about exposure status

Might be more thorough in interviewing on a related topic if disease status is known

e.g. smoking history in those with lung cancer

Question 18

What is recall bias?

Answer 18

When people become ill they are more likely to think hard about how past experiences have affected them

e.g. more likely to remember a brief period of smoking many years ago if you have been diagnosed with lung cancer

Question 19

What is non-differential misclassification?

Answer 19

When exposure status is misclassified but equally among controls and cases

Errors in determining outcome in controls and cases

Bias always towards the null

Question 20

What is differential misclassification?

Answer 20

Misclassification of exposure is not equal between cases and controls