Flashcards in Behavioral Sciences Deck (109)
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1
Relative Risk
Equation
When is it used?
What is it?
[a/(a+b)]/[c/(c+d)]
Cohort Studies
(Risk of developing disease in exposed group)/(risk in unexposed group)
2
Odds Ratio
Equation
When is it used?
What is it?
ad/bc
Case-Control Studies
Odds that the group with the disease was exposed to risk factor (a/c)/(Odds that the group without disease was exposed (b/d)
3
Observer Bias
Investigator is affected by prior knowledge
4
Confounding
Exposure-disease relationship can be explained by another variable
5
Lead-Time Bias
Apparent prolongation of survival because of earlier diagnosis
6
Recall Bias
Inaccurate pt recall
7
Selection Bias
Subjects selected biasedly or biased from selective loss of follow up
8
Case Control Study
Mode of investigation
Timeframe
Design
Basic Question
Measurement
Observational
Retrospective
Compare groups of people w/ and w/o disease and look for prior exposure or risk factors
"What Happened?"
Odds Ratio
9
Cohort Study
Mode of investigation
Timeframe
Design
Basic Question
Measurement
Observational
Prospective or Retrospective
Compare a group with a given exposure or risk factor to a group w/o it and look if exposure ↑ likelihood
Who will or Who has developed disease
Relative Risk
10
Cross Sectional Study
Mode of investigation
Timeframe
Design
Basic Question
Measurement
Observational
Right Now
Collect data from a group of people to assess frequency of disease and relative risk at a particular point in time
"What is happening?"
Prevalence, Relative Risk, Can show Risk Factor Association but not causality
11
Twin Concordance Study
Design
Measurements
Compares frequency with which monozygotic or dizygotic twins develop the same disease
Measures Heritability
12
Adoption Study
Design
Measurements
Compares siblings raised by biological vs adoptive parents
Heritability and influence of environmental factors
13
Clinical Trial
Population involved
Design
What improves study
Experimental study involving humans
Compares therapeutic benefits of 2 or more treatments or treatment and placebo
Randomized, Controlled, and Double Blinded studies are better
14
Double vs Triple Blind
Double: Patients and Doctors do not know whose getting treatment
Triple: Researchers analyzing data do not know who got treatment
15
Phase I Clinical Trial
Sample
Purpose
Small # of health volunteers
Assesses safety, toxicity, and pharmacokinetics
16
Phase II Clinical Trial
Sample
Purpose
Small # of patients w/ disease
Assesses treatment efficacy, optimal dosing, and adverse effects
17
Phase III Clinical Trial
Sample
Purpose
Large # of patients comparing 2 drugs or placebo
Compares new treatment to current treatment
18
Phase IV Clinical Trial
Sample
Purpose
Postmarketing surveillance trial of patients after approval
Detects rare or long term adverse effects
19
Sensitivity
Rate of what?
Formula (2)
Purpose
Use
"SNOUT - SeNsitivity rules OUT"
"PID - Positive In Disease"
True Positive Rate
a/(a+c) = 1-(false neg rate)
Rules out disease
Used for screening in diseases w/ low prevalence
20
Specificity
Rate of what?
Formula (2)
Purpose
Use
"SPIN - SPecificity rules IN"
"NIH - Negative In Health"
True Negative Rate
d/(d+b) = 1-(false pos rate)
Rules in disease
Confirmatory test after positive screening test
21
Positive Predictive Value
What does it show?
Formula
What does it vary with?
Proportion of + tests that are true positives
a/(a+b)
Varies directly with prevalence or pretest probability: high pretest probability --> high PPV
22
Negative Predictive Value
What does it show?
Formula
What does it vary with?
Proportion of negative test results that are true negative
d/(c+d)
Varies inversely with prevalence or pretest probability: High pretest probability --> low NPV
23
Incidents
(New cases over specified period)/(Population at risk)
24
Prevalence Equations (2)
(Existing cases)/(Population at risk)
Incidence x Average disease duration
25
Prevalence vs Incidence in chronic disease
Prevalence > Incidence
26
When are RR and OR equal?
When prevalence is low
27
Attributable Risk
Equation
What is it?
[a/(a+b)]-[c/(c+d)]
Risk in exposed group - Risk in unexposed group
28
Absolute Risk Reduction (ARR)
What is it?
c/(c+d) - a/(a+b)
Event rate in placebo minus treatment groups
29
Number Needed to Treat
What is it?
Equation
Number of pts who need to be treated for 1 patient to benefit
1/(absolute risk)
30
