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828 > Causality and Study Designs > Flashcards

Causality and Study Designs Flashcards

1
Q

Association

A
  • Relationship between two or more variables

- Does not automatically mean that one variable is the cause of change in another

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2
Q

Causation

A

-One event is the result of the occurrence of the other event

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3
Q

Determining Causality

A
  • Answer about the relationship between a possible cause/exposure (independent) and an outcome (dependent)
  • Bradford-Hill’s criteria for causality are used to help decide if a variable contributed to an outcome
  • Study designs differ to the degree that they meet Bradford-Hill criteria
  • Higher level study designs provide stronger evidence for causality
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4
Q

Temporality

A

-Cause must precede effect

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5
Q

Reproducibility/Consistency

A

-Same results with different populations and study designs

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6
Q

Strength

A
  • Of association (or effect size)

- Bigger/stronger is better

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7
Q

Specificity

A
  • Nothing else causes this

- Nothing else is caused by this

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8
Q

Dose-response/Biological Gradient

A
  • Higher dose produces greater effect
  • Lower dose produces lower effect
  • Offending agent is discontinued and effect ceases
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9
Q

Biological Plausibility

A

-Relationship makes biological sense

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10
Q

Coherence

A

-Data doesn’t conflict with known facts

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11
Q

Analogy

A
  • Drug class effects

- Structural similarities

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12
Q

Evidence Hierarchy for Study Designs

A
  1. Meta Analyses
  2. Systematic Reviews
  3. Randomized Controlled Trials
  4. Cohort studies
  5. Case-control studies
  6. Case reports/case series
  7. Clinical textbooks/expert opinions
  8. Animal Research
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13
Q

Interpreting Evidence Hierarchy

A
  • Observation vs experimental conditions
  • Lower position: lower level evidence (expert opinion, case report, case series, cross-sectional)
  • Moderate level: evidence associated with case-control and cohort studies
  • Highest levels: done by RCT, systematic reviews, and meta-analyses
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14
Q

Observational Studies

A
  • Exposure not under investigator’s control; only observe
  • Case reports/case series
  • Cross-sectional
  • Case-cohort
  • Cohort
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15
Q

Experimental Studies

A
  • Investigators control the intervention

- Randomized controlled trial

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16
Q

Case reports/Case Series

A
  • Description of unique events in 1 patient (case report) or >= 2 patients (case series)
  • Weakest forms of evidence: small patient numbers, no control group, many biases possible
  • Good for: new conditions, novel treatments, adverse drug events, toxic exposures
  • Should include literature review to provide context for the port and detailed information on the clinical course/follow-up of patients
17
Q

Cross-Sectional

A
  • Descriptions of observations
  • Larger sample sizes than case studies/series
  • Can measure associations between variables (which came first/compounded?)
  • Good for measuring prevalence in a population at a SINGLE time point
  • Evidence quality dependent on data source
18
Q

Case-Control

A
  • Start with patients who already have a condition/outcome and look back in time for etiologies/risk factors that could’ve causes that outcome
  • Control group, contains similar people who didn’t experience that outcome
  • Compare cases versus controls for differences in characteristics/exposures
19
Q

Case-Control Uses

A
  • Strength of association is measured by Odds ratio
  • CANNOT prove causality
  • Good for investigating possible etiologies or risk factors for uncommon conditions
20
Q

Cohort

A
  • Prospective/retrospective
  • Already exposed to a suspected cause/risk factor and follow them forward to see outcome
  • Large groups of individuals
  • Can compare rates of an outcome for patients with and without the exposure (control)
  • Relative risk reflects the strength of association
  • Can demonstrate temporality
  • Good for establishing risk factors for an outcome and calculating incidence
21
Q

Prospective

A

Start at the present time and follow into future

22
Q

Retrospective

A

Start at a past time and follow to the present

23
Q

Randomized Controlled Trial (RCT)

A
  • Experimental design
  • Investigators control the intervention and follow patients prospectively to measure outcome
  • Decide who can/can’t participate
  • Patients are randomized into experimental and controlled
  • Minimize biases/confounders by study design
  • Good for establishing a good standard’s efficacy
  • Can demonstrate causality
  • Has strength of association, temporality, and dose-response
24
Q

Evidence Hierarchy + Causality

A
  • Ability to establish causation follows the evidence hierarchy
  • Case-control shows association between suspected cause and outcome of interest
  • Cohort shows association and establishes temporality
  • RCT shows association, establishes temporality, AND demonstrates dose-response

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