Inferring Causation

Question 1

What are the strengths and weaknesses of a “review” article?

Answer 1

Strengths - good discussion from experts in the field

Weak - subject to bias of author or journal

Question 2

Why are systematic reviews better than “reviews”?

Answer 2

They follow a prescribed protocol

Question 3

Where do you find systematic reviews? (3)

Answer 3

Peer-reviewed journals, databases, Cochrane Library

Question 4

Our research question is defined using PICO. What does each letter mean?

Answer 4

P_ - people of interest (patient); is the group or person similar to the patient?
I - Intervention; treatment, exposure, other agent
C - compare different treatments
O - outcome, is the outcome relevant to our patient? Is this what the patient wants to happen

Question 5

What are the two main goals someone has when writing a systematic review, to put together and present to the reader?

Answer 5

Increase sensitivity (detect an article when it exists) and reduce author bias.

Question 6

Publication bias

Answer 6

Bias towards publishing only significant outcomes. What if not significant? Want to include those too.

Question 7

Which experiments tend to have better effect sizes? (More significant results) weaker or stronger?

Answer 7

Weaker

Question 8

How are results of a systematic review summarized?

Answer 8

Forest plot form.

Question 9

Difference btwn meta-analysis and systematic review

Answer 9

Studies are combined in meta-analysis and analyzed. SR - just a compilation and presentation.

Question 10

Do causal processes involve intermediate steps?

Answer 10

Almost always

Question 11

What do we use to counter the persistent single-cause model?

Answer 11

Web of causation.

Question 12

For impact on web of causation, how many strands do you need to cut for impact?

Answer 12

Only at least 1

Question 13

Causes are necessary and/or sufficient. What does necessary mean?

Answer 13

Necessary - without the cause, the effect would not exist. Need more factors for effect to happen.

Question 14

What does sufficient mean?

Answer 14

If the cause is there, the effect will result, whether other causes are there or not.

Question 15

Name two examples of statistical numbers we use to assess association, or risk of outcome given exposure?

Answer 15

Risk ratio, odds ratio

Question 16

B-H criteria - what is the only required criteria?

Answer 16

Temporality,

Question 17

Strong associations from a well designed study are more or less likely to be caused by chance or bias?

Answer 17

Less

Question 18

To infer causality, what is required of the dose-response curve?

Answer 18

Strong association (change one, change the other), doesn’t need to be linear

Question 19

What is the B-H criteria of reversibility?

Answer 19

Take the cause away, effect goes away.

Question 20

What is the B-H criteria of consistency?

Answer 20

The association (or cause and effect) are seen across multiple groups - they haev high external validity.

Question 21

What is the B-H hill criteria of biological plausibility to determine cause & effect?

Answer 21

The association should be possible and explainable.

Question 22

What is the B-H criteria of specificity for inferring causation?

Answer 22

One exposure, one outcome.

Question 23

What is the analogy criteria for the B-H criteria for inferring causality?

Answer 23

The cause and effect relationship are similar to those that already exist.

Question 24

Is the B-H criteria a checklist? How does one establish causality

Answer 24

No - the more criteria, the stronger the case

Question 25

Ecologic studies

Answer 25

Study a sample population for associations in question

Question 26

Ecologic fallacy

Answer 26

Applying the results of a group to an individual

Question 27

What is the best use of an ecologic study?

Answer 27

Generating a hypothesis from an idea and moving forward from there.