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19 Cards in this Set
- Front
- Back
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What are the 2 fundamental questions when analyzing data on risk factors for disease?
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1) How strong is the evidence in supporting an association?
-what is the likelihood that we could have seen these results by chance alone? ---->*STATS!!! 2) What is the effect size? i.e. HOW IMPORTANT is this factor in causing disease? --->RISK ANALYSIS!! |
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What is the clinical question regarding relative risk?
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How much more likely are exposed individuals to *become diseased relative to unexposed?
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What is the source data for determining relative risk?
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Cohort studies & randomized trials
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What is the definition of relative risk?
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= risk in exposed/ risk in unexposed
= incidence in exposed/ incidence in unexposed |
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What does relative risk measure?
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The strength of association* between exposure & disease
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What does a relative risk of 1 mean?
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Risk in exposed is equal to risk in unexposed: no association of exposure w/ disease
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What does a relative risk > 1 mean?
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Risk in exposed is greater than risk in unexposed: positive association with possible causal
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What does a relative risk < 1 mean?
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Risk in exposed group is smaller than risk in unexposed: negative association; possibly protective
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How do you assess a relative risk of 0.5 when comparing a new dewormer (exposed) and an old dewormer (unexposed)?
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Means that the animals getting the new dewormer were half as likely to get worm infections over the time period compared to the old drug
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What is the clinical question posed with attributable risk (..in an exposed group)?
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What is the incidence of disease attributable to exposure?
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What does attributable risk measure?
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Relative importance* of exposure to a given factor, compared to all other factors that contribute to disease causation
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Incidence in the exposed group = _________ + _________
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Incidence NOT due to the exposure (background incidence) + incidence due to the exposure
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Incidence in the nonexposed group =_________
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Incidence not due to the exposure (background incidence)
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What is the definition (equation) of attributable risk?
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AR= risk in exposed- risk in unexposed
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How do you calculate the fraction* of disease attributable to exposure (AF)?
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AF= AR/ risk in exposed
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How do you calculate how many patients must be treated to prevent one case (number needed to treat- NNT)?
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NNT= 1/ AR
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What does a negative attributable risk tell you?
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Tells you the factor prevents not causes disease
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What does an attributable risk of -0.055 mean, in the context of comparing vaccinated cats & felV Vs non vaccinated cats?
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Cats are 5.5% more likely to get FelV if they are not vaccinated
- for every 100 kittens you vaccinate you're avoiding 5.5 cases from developing |
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What does relative risk measure? Attributable risk?
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Relative risk: a measure of the strength of association
Attributable risk: measure of relative importance of a risk factor & its potential as a target for disease prevention |
