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PHRM 100 – PPHC > PPHC 08 and 09: Evidence Evaluation (Epidemiology) – What are features of observational studies? > Flashcards

PPHC 08 and 09: Evidence Evaluation (Epidemiology) – What are features of observational studies? Flashcards

1
Q

What are the three types of epidemiology?

A
  • descriptive (observational)
  • analytic (observational)
  • experimental
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2
Q

What is the goal of descriptive epidemiology?

A

to examine patterns (of disease, health behaviours)

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3
Q

What is the goal of analytic epidemiology?

A

to evaluate relationships between risk/protective factors and disease

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4
Q

What is the goal of experimental epidemiology?

A

to evaluate effect of treatment/intervention on disease

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5
Q

What are the 2 types of experimental studies?

A
  • randomized controlled trial
  • non-randomized
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6
Q

What are the 2 types of observational studies?

A
  • descriptive
  • analytic
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7
Q

What are the 3 types of descriptive observational studies?

A
  • case report
  • case series
  • cross-sectional
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8
Q

What are the 3 types of analytic observational studies?

A
  • cross-sectional
  • cohort
  • case-control
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9
Q

What are observational studies?

A

individuals are followed ‘observed’ in real-world settings

  • no intervention/exposure assignment by researcher
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10
Q

What is the goal of descriptive vs. analytic observational studies?

A
  • descriptive: examine patterns (of exposure or outcome)
  • analytic: evaluate relationship (between exposure and outcome)
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11
Q

Do descriptive vs. analytic observational studies evaluate an intervention?

A
  • descriptive: no
  • analytic: yes – assigned by researcher
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12
Q

Is there a hypothesis at the start of descriptive vs. analytic observational studies?

A
  • descriptive: no hypothesis
  • analytic: defined hypothesis
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13
Q

Is there a hypothesis at the end of descriptive vs. analytic observational studies?

A
  • descriptive: possible hypothesis
  • analytic: confirm or reject hypothesis
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14
Q

What are descriptive observational studies?

A

describe occurrence of an outcome (ie. disease)

  • do not evaluate an intervention
  • ‘hypothesis generating’ – no hypothesis at start, then possible hypothesis at end
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15
Q

What are case reports?

A

detailed presentation of 1 case (n of 1)

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16
Q

What do case reports do? (4)

A
  • report a new or unique condition
  • describe previously undescribed disease
  • show unexpected new therapeutic effect
  • report adverse events

(same as case series)

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17
Q

What do case reports NOT do? (3)

A
  • measure disease incidence (describe prevalent disease)
  • identify risk factors
  • identify cause of disease

(same as case series)

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18
Q

What are case series?

A

detailed presentation of 2 or more cases

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19
Q

What do case series do? (4)

A
  • report a new or unique condition
  • describe previously undescribed disease
  • show unexpected new therapeutic effect
  • report adverse events

(same as case reports)

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20
Q

What do case series NOT do? (3)

A
  • measure disease incidence (describe prevalent disease)
  • identify risk factors
  • identify cause of disease

(same as case series)

21
Q

What are cross-sectional studies?

A

observational study design that surveys exposures and/or outcomes at a single point in time (snapshot)

22
Q

What type of study are cross-sectional studies?

A

analytic – ie. measure association between exposure and disease

  • evaluate association between exposure and outcome
  • temporal sequence of exposure and outcome impossible to determine (don’t know which occurred first) – main limitation compared to cohort and case-control studies

descriptive – ie. focus on exposure or disease

  • examines patterns (of disease, health behaviours)
  • measures prevalence, not incidence
23
Q

What are analytic observational studies?

A

describe relationship between exposure and outcome

  • disease can be the exposure or outcome
  • can evaluate an intervention – though not assigned by researcher
24
Q

Analytic Observational Studies

What is the exposure?

A
  • drug (ie. statin)
  • intervention (ie. diet)
  • policy (ie. drug plan coverage
25
Q

Analytic Observational Studies

What is the outcome?

A
  • clinical measure (ie. cholesterol)
  • disease outcome (ie. occurrence of cancer)
  • patient satisfaction
26
Q

What are key concepts for analytic epidemiologic studies?

A
  • population: who we want to learn about
  • sample: who we will study
27
Q

Analytic Cross-Sectional Study

What is an analytic cross-sectional study?

A

observational study design that surveys exposures and/or outcomes at a single point in time (snapshot)

28
Q

Analytic Cross-Sectional Study

What are the 4 analyses?

A
  • A: exposed, have outcome
  • B: exposed, no outcome
  • C: not exposed, have outcome
  • D: not exposed, no outcome
29
Q

Analytic Cross-Sectional Study

Why can’t you measure the risk of an outcome?

A

because we don’t know when outcome occurs

  • exposure and outcome are assessed at the same time in analytic cross-sectional study
  • therefore relevant concept is odds
30
Q

What is odds?

A

ratio of the number of ways the event can occur to the number of ways the event cannot occur

odds = event / (1 - event)

31
Q

What is odds ratio?

A

measure of association

odds ratio = (odds of outcome among exposed) / (odds of outcome among unexposed) = (a/b) / (c/d)

32
Q

What is OR > 1?

A

association

  • exposed group have higher odds of outcome compared to unexposed group
  • % increase = (OR - 1) x 100
33
Q

What is OR = 1?

A

no association

34
Q

What is OR < 1?

A

inverse association

  • exposed group have lower odds of outcome compared to unexposed group
  • % decrease = (1 - OR) x 100
35
Q

Cohort Study – Analytical Observational Study

What is the starting point of a cohort study?

A

exposure

36
Q

Cohort Study – Analytical Observational Study

What are the 3 steps of a cohort study?

A
  • draw study sample from population
  • identify exposure status (exposed vs. not exposed)
  • follow individuals over time to see who develops outcome
37
Q

Cohort Study – Analytical Observational Study

What is the key to cohort studies?

A
  • outcome occurs after exposure
  • participants are followed up to that outcome(s) so researchers know when that outcome(s) occurred
38
Q

What is relative risk/risk ratio (RR)?

A

measure of association

relative risk = (risk of outcome among exposed) / (risk of outcome among unexposed) = a/(a+b) / c/(c+d)

39
Q

What is RR > 1?

A

association

  • Exposed group have higher risk of outcome than unexposed group
  • % increase = (RR - 1) x 100
40
Q

What is RR = 1?

A

no association

41
Q

What is RR < 1?

A

inverse association

  • exposed group have lower risk of outcome than unexposed group
  • % decrease = (1 - RR) x 100
42
Q
A
43
Q

Case-Control Study – Analytical Observational Study

What is the starting point for case-control studies?

A

outcome (ie. disease)

43
Q

Case-Control Study – Analytical Observational Study

What are the steps to case-control studies?

A
  • identify cases (individuals with outcome or disease)
  • identify controls (individuals without the outcome or disease or interest) – note: cases and controls usually match on some factors or characteristics (ie. age, gender)
  • look at exposure histories
44
Q

Case-Control Study – Analytical Observational Study

When might case-control studies be used?

A

when outcome (case) is rare

45
Q

Case-Control Study – Analytical Observational Study

What measure of association does case-control studies use?

A

odds

46
Q

Case-Control Study – Analytical Observational Study

Why is it important to analyze case-control studies?

A

cannot measure risk of an outcome because we don’t know when outcome occurs

  • case-control study design does not involve follow-up
  • in case-control study, one starts at the outcome
  • so relevant concept is odds
47
Q

What is the problem with mis-labelling ‘case-control’?

A

‘case-control’ refers to design of the study, but is often confused with ‘cases’ and ‘controls’ which refer to participants in a study

PHRM 100 – PPHC (18 decks)

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