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Study Designs Flashcards

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1
Q

Cohort Study: Starts with?

A

Exposure

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2
Q

Cohort Study: Main Measures?

A

RR, AR

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3
Q

Cohort Study: Good For?

A

Rare exposures

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4
Q

Cohort Study: Main Bias?

A

Attrition

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5
Q

Case-Control Study: Starts with?

A

Outcome

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6
Q

Case-Control Study: Main Measures?

A

OR

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7
Q

Case-Control Study: Good For?

A

Rare outcomes

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8
Q

Case-Control Study: Main Bias?

A

Recall, Selection

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9
Q

Cross-sectional Analytical Study: Starts with?

A

Both exposure and outcome at a single point in time

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10
Q

Cross-sectional Analytical Study: Main Measures?

A

OR, PRR

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11
Q

Cross-sectional Analytical Study: Good For?

A

Quick prevalence estimation

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12
Q

Cross-sectional Analytical Study: Main Bias?

A

None specific (but cannot determine causality)

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13
Q

RCT (Experimental) Study: Starts with?

A

Randomization

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14
Q

RCT (Experimental) Study: Main Measures?

A

RR, efficacy

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15
Q

RCT (Experimental) Study: Good For?

A

Interventions

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16
Q

RCT (Experimental) Study: Main Bias?

A

Selection, Information (if not blinded)

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17
Q

Descriptive Studies: Purpose?

A

Ask WHAT, WHO, WHERE, WHEN

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18
Q

Analytical Studies: Purpose?

A

Ask WHY (causation)

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19
Q

Exposure (Definition)

A

Possible cause/risk factor

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20
Q

Outcome (Definition)

A

Disease/effect

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21
Q

Confounding factor (Definition)

A

Third variable distorting the true exposure-outcome association

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22
Q

Cohort Study (Recruitment Basis)

A

Exposure status

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23
Q

Cohort Study (Best Use Case)

A

Rare exposures, multiple outcomes from one exposure

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24
Q

Cohort Study (Key Measures)

A

Relative Risk (RR), Attributable Risk (AR), Incidence

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25
Cohort Study (Main Biases)
Selection bias, Attrition (loss to follow-up)
26
Cohort Study (Key Feature)
Participants are outcome-free at the start
27
Case-Control Study (Recruitment Basis)
Outcome (disease) status
28
Case-Control Study (Best Use Case)
Rare outcomes (diseases), multiple exposures for one outcome
29
Case-Control Study (Key Measure)
Odds Ratio (OR)
30
Case-Control Study (Main Biases)
Selection bias, Recall bias, Interviewer bias
31
Case-Control Study (Key Feature)
Always retrospective regarding exposure history
32
Cross-Sectional Analytical Study (Recruitment Basis)
Simultaneously assesses exposure and outcome
33
Cross-Sectional Analytical Study (Best Use Case)
Prevalence surveys, quick assessments
34
Cross-Sectional Analytical Study (Key Measures)
Odds Ratio (OR), Prevalence Rate Ratio (PRR), Prevalence
35
Cross-Sectional Analytical Study (Key Limitation)
Cannot determine causality (temporality unclear)
36
Randomized Controlled Trial (RCT) (Recruitment Basis)
Random allocation to intervention or control group
37
RCT (Best Use Case)
Testing interventions (efficacy/effectiveness)
38
RCT (Key Measures)
Relative Risk (RR), Attributable Risk (AR), Efficacy
39
RCT (Main Biases)
Selection bias (if randomization fails), Observer bias (if not blinded), Information bias (if not blinded)
40
RCT (Key Features)
Gold standard for causality
41
Incidence (Definition)
Number of new cases of a disease in a population over a specific period of time
42
Prevalence (Definition)
Total number of existing cases of a disease in a population at a specific point in time
43
Relative Risk (RR) (Formula/Interpretation)
Incidence (exposed) / Incidence (unexposed)
44
Attributable Risk (AR) (Formula/Interpretation)
Incidence (exposed) - Incidence (unexposed)
45
Odds Ratio (OR) (Formula/Interpretation)
Odds of exposure (cases) / Odds of exposure (controls)
46
Prevalence Rate Ratio (PRR) (Formula/Interpretation)
Prevalence (exposed) / Prevalence (unexposed)
47
Selection Bias (Definition)
Systematic error in the selection or retention of study participants leading to a distorted association
48
Information Bias (Definition)
Systematic error in the measurement of information on exposure or outcome (e.g., Recall Bias, Interviewer Bias)
49
Confounding Bias (Definition)
Distortion of the exposure-outcome association by a third variable related to both
50
Methods to Reduce Bias?
Randomization, Matching, Blinding, Standardization, Restriction, Stratified Analysis
51
Randomization (RCT Definition)
Process of assigning subjects to treatment or control groups by chance to minimize selection bias and confounding
52
Single Blinding (RCT)
Subject doesn't know their group allocation
53
Double Blinding (RCT)
Subject AND Investigator don't know group allocation
54
Triple Blinding (RCT)
Subject, Investigator, AND Data Analyst don't know group allocation
55
Placebo (RCT Definition)
An inert substance or procedure given to the control group to mimic the active intervention
56
Evidence-Based Medicine (EBM) (Definition)
Integration of the best research evidence with clinical expertise and patient values
57
PICO (Clinical Questions)
Framework for asking clinical questions: Patient/Population, Intervention, Comparison, Outcome
58
Hierarchy of Evidence (Therapy/Intervention)
1. Systematic Reviews/Meta-Analyses of RCTs, 2. RCTs
59
Hierarchy of Evidence (Prognosis/Risk Factors)
1. Systematic Reviews of Cohort Studies, 2. Cohort Studies
60
Hierarchy of Evidence (Rare Outcomes/Diseases)
Case-Control Studies
61
Cohort Study (Quick Tip Summary)
Good for rare exposures, calculating incidence, studying multiple outcomes
62
Case-Control Study (Quick Tip Summary)
Good for rare diseases, studying multiple exposures, relatively quick and inexpensive
63
Cross-Sectional Study (Quick Tip Summary)
Good for estimating prevalence, quick and easy, hypothesis generation
64
RCT (Quick Tip Summary)
Strongest design for inferring causality, minimizes bias and confounding
65
Fundamental Principle of Causality in Epi Studies
Exposure must precede the outcome
66
Study Purposes in Epidemiology
Determine disease magnitude, Identify risk factors, Evaluate interventions
67
Descriptive vs Analytical Approach
Descriptive (What, Who, Where, When) vs Analytical (Why, How - tests hypotheses)
68
Solving Confounding?
Randomization (RCTs), Restriction, Matching, Stratified Analysis, Multivariate Analysis
69
General Steps in an Epidemiological Study
Define problem, Set objectives, Choose design, Sampling, Implement, Analyze, Interpret
70
Case Report (Description)
Detailed description of a single patient case
71
Case Report (Advantage/Disadvantage)
Useful for rare/new diseases / Limited generalizability
72
Case Series (Description)
Description of characteristics of a group of patients with the same disease/exposure
73
Case Series (Advantage/Disadvantage)
Hypothesis generation / No comparison group
74
Cross-sectional (Descriptive) Study (Description)
Measures exposure and outcome prevalence at a single point in time ("snapshot")
75
Cross-sectional (Descriptive) Study (Advantage/Disadvantage)
Quick, estimates prevalence / Cannot determine cause-effect sequence
76
Correlational (Ecological) Study (Description)
Compares disease frequencies between populations based on aggregate data
77
Correlational (Ecological) Study (Advantage/Disadvantage)
Hypothesis generation, uses existing data / Ecological fallacy (cannot infer individual risk from group data)
78
Descriptive Studies Describe Variation By?
Person (age, sex, ethnicity, SES), Place (geographic location), Time (trends, seasonality)
79
Cohort Study (Prospective vs Retrospective)
Prospective (starts now, follows into future) / Retrospective (uses past records to identify exposure and follow to present outcome)
80
Cohort Study (Steps)
1. Select exposed & unexposed groups, 2. Ensure all are outcome-free initially, 3. Follow over time, 4. Ascertain outcome status
81
Case-Control Study (Steps)
1. Select cases (with disease) & controls (without disease), 2. Measure past exposure history in both groups, 3. Calculate OR
82
Berkesonian Bias
A form of selection bias specific to case-control studies conducted in hospitals, where exposure may increase risk of admission itself.
83
Incidence (Used in which designs?)
Cohort, RCT
84
Prevalence (Used in which designs?)
Cross-sectional
85
Relative Risk (RR) (Used in which designs?)
Cohort, RCT
86
Attributable Risk (AR) (Used in which designs?)
Cohort, RCT
87
Odds Ratio (OR) (Used in which designs?)
Case-Control, Cross-sectional, (Can estimate RR in Cohort/RCT if outcome is rare)
88
Prevalence Rate Ratio (PRR) (Used in which designs?)
Cross-sectional
89
Preventing Selection Bias?
Randomization (RCT), Careful selection of controls (Case-Control), High follow-up rates (Cohort)
90
Preventing Information Bias?
Blinding, Standardized measurement protocols, Objective measures, Careful questionnaire design
91
Preventing Confounding Bias?
Randomization (RCT), Restriction, Matching, Stratification/Adjustment in analysis
92
RCT (Placebo Purpose)
Controls for the psychological effect of receiving an intervention
93
RCT (Blinding Purpose)
Reduces observer bias and participant expectation effects
94
Case-Control vs Cohort (Recruitment)
Outcome (Disease) vs Exposure
95
Case-Control vs Cohort (Best for)
Rare Outcomes vs Rare Exposures
96
Case-Control vs Cohort (Bias Risk)
Recall/Selection vs Loss to Follow-up/Selection
97
Case-Control vs Cohort (Time/Cost)
Shorter/Cheaper vs Longer/More Expensive
98
Case-Control vs Cohort (Main Measure)
Odds Ratio (OR) vs Relative Risk (RR), Attributable Risk (AR)
99
Ecological Fallacy
Erroneous assumption that associations observed at the group level hold true at the individual level
100
Recruitment based on
Case Control: Outcome Prospective Cohort: Exposure
101
Better to study
Case Control: Rare outcomes Prospective Cohort: Rare exposure
102
Can study
Case Control: Many exposures Prospective Cohort: Many outcomes
103
Main Bias
Case Control: Recall bias Prospective Cohort: Loss to follow up (attrition bias)
104
Duration
Case Control: Lesser Prospective Cohort: Longer
105
Expense
Case Control: Lesser Prospective Cohort: More
106
Measures of risk
Case Control: Odds ratio (OR) Prospective Cohort: RR / AR
107
Study Direction
Case Control: Retrospective (backward / past) Prospective Cohort: Prospective (future / forward)
108
Participant Comparison
Case Control: Compare risk factors in diseased & non-diseased; Compare frequency of exposure among cases & controls Prospective Cohort: Exposed & unexposed participants; Disease free at start
109
Incidence Calculation
Case Control: Cannot calculate disease incidence (not a disease free population at first) Prospective Cohort: Measures incidence

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