Causality

Question 1

Who created the postulates of determining that a disease was caused by a bacteria?

Answer 1

Robert Koch 1890

Question 2

What are Koch’s postulates?

Answer 2

Consistency
Specificity
Biological coherence
Predictive or experimental performance

Question 3

Explain consistency re Koch

Answer 3

Agent must be shown to be present in every case of the disease by isolation in pure culture

Question 4

What is Koch’s specificity?

Answer 4

Agent must not be found in the case of another disease

Question 5

What is Koch’s biological coherence?

Answer 5

Once isolated, the agent must be capable of reproducing the disease in experimental animals

Question 6

What is Koch’s predictive performance?

Answer 6

The agent must be recovered from the experimental disease produced

Question 7

What criteria of causality can be used?

Answer 7

Koch
Bradford Hill
Susser
Rothman’s Sufficient
Web of causation

Question 8

What is Bradford Hill’s criteria of causality?

Answer 8

Temporal association
Dose-response association
Specificity
Consistency
Plausible biological association
High strength of oassociation
Absence of reverse causality

Question 9

Susser’s categories of causation

Answer 9

Strength
Specificity - in cause and effect
Consistency
Predictive Performance
Coherence/plausability

Question 10

How can one measure Susser’s consistency?

Answer 10

Replicability

Question 11

Subcategories of Susser’s Coherence category?

Answer 11

Theoretical
Factual
Biological
Statistical

Question 12

Essential categories of Susser’s causality

Answer 12

Association
Direction of prediction
Time order

Question 13

How is Susser’s association category judged?

Answer 13

By strength of probabilities based on preset expectations of chance occurrences and consistency upon replication.

Question 14

Explain Susser’s category of Direction of Prediction

Answer 14

Change in one state assumed to be the effect must be consequent on change in independent antecedent states presumed to be the cause.

Question 15

Which essential criteria of Sussers is more critical in defining causality?

Answer 15

Direction of Prediction

Question 16

Explain Susser’s time order category

Answer 16

Reversal of time order assures elimination of putative cause

Question 17

What is sufficient cause?

Answer 17

Minimal set of conditions that produce an outcome rather than just one

Question 18

In which studies does one see sufficient cause

Answer 18

Epidemiology

Question 19

What makes up sufficient cause?

Answer 19

Component cause

Question 20

Importance of component cause

Answer 20

Outcome will not occur by a causal pathway if any of the components are missing

Question 21

Why is the idea of component cause relevant to public health?

Answer 21

Suggests that it is not necessary to identify all of the component causes to prevent a disease outcome

Question 22

What is a necessary cause?

Answer 22

A component cause that must be present in every sufficient cause for the outcome

Question 23

What terms are associated with Rothman’s Sufficient Model?

Answer 23

Sufficient cause
Component cause
Necessary cause

Question 24

Who created the term web of causation?

Answer 24

MacMahon and Pugh in 1960

Question 25

What was web of causation used to describe?

Answer 25

Complexity of the relationship among antecedents when investigating cause of disease

Question 26

What is the concept in web of causation?

Answer 26

Mutual interactions among risk factors which have both direct and indirect effects on outcomes.

Question 27

Who expanded the web of causation?

Answer 27

Murray and Lopez

Question 28

What did Murray and Lopez do to the web of causation?

Answer 28

Separated proximal risk factors from distal

Question 29

What are proximal risk factors?

Answer 29

Established pathophysiological mechanisms

Question 30

What are distal risk factors?

Answer 30

Based on empirical evidence

Question 31

What is another name of the model Murray and Lopez created from the web of causation?

Answer 31

Hierarchical causal model

Question 32

How can positive result from a study be explained?

Answer 32

Selection differences between two groups Measurement differences between two groups Confounding factors causing indirect association Chance causing spurious association (Type 1 error) Presence of true causal assocation

Question 33

What is the independent variable?

Answer 33

The one which is having the effect

Question 34

What is the dependent variable?

Answer 34

Outcome of interest

Question 35

What criteria are needed for a characteristic to be a confounder?

Answer 35

Must be related to exposure in some way Must be related to outcome in terms of prognosis or susceptibility Will not be on causal pathway between exposure and outcome Distribution of characteristic must be different in groups compared (mean or standard deviation)

Question 36

What is needed to withstand confounding effects in analytical studies?

Answer 36

Systematic effort to identify and measure potential confounders Data on distribution of potential confounders across groups must be available

Question 37

Methods to control confounders in design of study

Answer 37

Restriction Matching Randomisation

Question 38

Methods t control confounders in analysis of study

Answer 38

Stratification Multivariate methods

Question 39

What is restriction?

Answer 39

Avoid groups with significant confounding influence in study

Question 40

Disadvantages of restriction

Answer 40

Will limit sample size

Question 41

What is matching?

Answer 41

Make sure confounders are equally distributed

Question 42

Impact of randomisation on confounders

Answer 42

Will ensure two groups are more likely to b similar in terms of confounder distribution

Question 43

What must one do if randomisation does not lead to equal distribution of confounders?

Answer 43

Consider stratification or multivariates

Question 44

Which design method helps control both known and unknown confounders

Answer 44

Randomisation only

Question 45

What is stratification?

Answer 45

Tabulate data for various categories of exposure to confounder separately and analyse variable influence

Question 46

What are multivariate methods?

Answer 46

Regression methods to analyse effect of various confounders.

Question 47

What do multivariate methods produce?

Answer 47

Adjusted rates and crude rates

Question 48

What is an effect modifier?

Answer 48

A third factor existing as a sub-group but nor related to outcome or exposure

Question 49

How can effect modifiers be eliminated?

Answer 49

Stratified analysis

Question 50

How do confounders result in bias?

Answer 50

Affect internal validity of a study