Measures Of Association Flashcards
What is the difference between sensitivity and specificity?
Sensitivity = ability to correctly identify those who actually have the disease (true positive)
Specificity = ability to correctly identify those who actually do NOT have the disease (true negative)
What is the difference between incidence rate and prevalence?
Incidence rate = # NEW cases of disease in a given time period
Prevalence = TOTAL # of cases of disease in a given time period
(Ie. If prevalence is the overall % pts with disease, incidence rate is inflow % of new pts with disease)
What is the difference between relative risk and attributable risk?
Relative risk = the ratio of the risk of disease in exposed individuals to the risk of the disease in unexposed individuals
Attributable risk = the proportion of disease incidence or risk that can be attributed to a specific exposure
TLDR: RR = focuses on the strength of the association between exposure and outcome, AR = focuses on the proportion of diseases in the exposed group that can be attributed to the exposure.
Define attack rate
of people exposed who got disease
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Total # of people exposed
measure of morbidity
Define mortality rate
The # of deaths from a cause in a specific population in a specific time frame
Define standardization, what is the difference between direct and indirect standardization?
Set of techniques used to remove the effects of intersubject variability when comparing ≥2 populations
Direct: Outcomes if the populations had the same age distributions as a standardized population
Indirect: compares rate of disease observed in populations to EXPECTED rate in standard population
Define “population-attributable risk”
The attributable risk for an ENTIRE population regardless of whether or not everyone was exposed
AKA = what is the impact of removing the exposure on the total population?
Ie. PAR% = 12% then making all people stop [exposure] would eliminate 12% of all [disease] in the population
Define number needed to treat (NNT)
Number of patients needed to treat in order to produce one BENEFICIAL outcome
Aka = lower number is better
Ie. Need to treat X people with drug to cure 1 person
Define number needed to harm (NNH)
Number of patients who receive treatment before one ADVERSE EFFECT occurs
Aka = higher number is better
Ie. Treated X people with drug before 1 person got [AE]
What is the equation for calculating SENSITIVITY?
(True positive)
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(True positive) + (False Negative) [aka all positives]
What is the equation for calculating SPECIFICITY?
(True negative)
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(True negative) + (False positive) [aka all negatives]
What is morbidity and what terms can describe it?
Morbidity = rate of disease in a population
Described by:
- cumulative incidence proportion
- Incidence rate
- Prevalence
- Attack rate
What is relative risk/risk ratio?
Ratio of the risk of disease in exposed individuals to the risk of the disease in unexposed individuals
- RR < 1: negative association/possible protective
- RR > 1: positive association/possible causal exposure
Compare RR vs OR
RR: compares subjects who got disease w/ exposure to total exposures vs subjects who got disease w/o exposure to total non-exposures
OR: compares all “expected” outcomes vs all “unexpected” outcomes (expected being exposure = disease, non-exposure = no disease)
What is the RR calculation?
[(exposed&disease)/(total exposed)]
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[(non-exposed&disease)/total non-exposed)]
