Epidemiology Flashcards
Define epidemiology
a public health discipline basic science which studies the distribution and determinants of disease in populations to control disease and illness and promote health
What are the 3 primary groupings in epidemiology?
disease; exposure; population
Who is the father of epidemiology?
John Snow
In regards to distribution of disease, what is the frequency of disease occurrence?
not only counts but also counts in relation to size of the population
What 3 aspects do patterns of disease occurrence encompass?
person; place; time
In regards to distribution of disease, Who/where/when = ____ epidemiology
descriptive
In regards to determinants of disease, why/how = ____ epidemiology
analytic
New occurrences of an outcome or disease is called what?
incidence
Existing occurrences of an outcome/disease is called what?
prevalence
note: includes old and new cases, collectively
(new cases of the outcome)/(# persons at risk of the outcome) = ?
incidence
note: always subtract out those who already have the disease
What is the equation for incidence rate?
new cases/ person time (total net time people were at risk)
Occurrence of disease clearly in excess of normal expectancy is called what?
epidemic
an epidemic limited to a localized increase in the occurrence of disease is called what?
outbreak
define endemic
the constant presence of a disease within a given area or population in excess of normal levels in other areas
define pandemic
an epidemic occurring over a very wide area involving a large number of people
Explain difference between quantitative and qualitative research design
quantitative = numbers qualitative = words
Explain difference between interventional and observational methodology
interventional = forced allocation to study groups
observational = no forced allocation to study groups
Explain the different phases of an interventional study
pre-clinical: bench research
phase 1: assess safety, small sample (20-80)
phase 2: assess safety and efficacy in diseased population, larger sample (100-300)
phase 3: primary focus is to assess efficacy, even larger sample (1000-3000)
Phase 4: post-marketing, long-term effects in large population
Define a single-blind interventional study
study subjects are not informed which intervention they are receiving but clinicians know
Define a double-blind interventional study
neither investigator nor study subjects are informed which intervention each subject is receiving
Define an open label interventional study
everyone knows everything
Inert treatments made to look identical in all ascents to the active treatment is called?
placebo
What is a double-dummy treatment?
more than 1 placebo used
What is the placebo-effect?
improvement in condition, by power of suggestion & due to the care being provided
What is the hawthorne-effect?
desire of study subject to “please” investigators by reporting positive results, regardless of treatment allocation
Group allocation in a cohort study is based on what?
exposure
Group allocation in a case-control study is based on what?
disease
What does a cross-sectional study examine?
the relationship between disease AND exposure
What is absolute risk reduction (ARR)?
subtract risks of two groups
What is relative risk reduction (RRR)?
ARR / Risk of unexposed
What is the number needed to treat?
1 / ARR
Interpret RR = 1.53
53% greater risk in the comparator group
Interpret RR = 0.73
27% lower risk of the outcome
When looking at the CI for ratios, if both values are on the same side of 1.0, is the data significant or not?
always significant
How do you test for confounding?
calculate crude RR and then calculate adjusted RR which controls for confounder. if there is a 10-15% difference, confounding is present
What is the purpose of controlling for confounding?
to get a more accurate estimate of the true association between exposure and disease
In regards to study design, what are three ways you can control confounding?
randomization, restriction, matching
In regards to analysis of data, what are 2 ways you can control confounding?
stratification, multivariate analysis
A 3rd variable, that when present, modifies the magnitude of effect of an association by varying it within different levels of a 3rd variable is called what?
effect modification
How is effect modification different from confounding?
comparing the crude estimate of the measure of association is not the only element used to evaluate the presence of effect modification, stream-specific estimates are compared directly to see if they are different. If the highest layer is 10-15% different than lowest layer, there is effect modification present
How do artifactual associations arise?
from significant bias and/or extensive confounding
How do non-causal associations occur?
- disease may cause exposure (RA leading to physical inactivity)
- disease and exposure are both associated with third factor (confounding)
What are Hill’s guidelines?
strength, consistency, temporality, biologic gradient, plausibility
Define True Positive
test is positive and patient does have disease (A box)
Define True Negative
Test is negative and patient does not have disease (D box)
Define False Positive
Test is positive but patient does not have disease
Define False Negative
Test is negative but patient does have disease
Sensitivity and specificity describe accuracy of ___ ___, while PPV and NPV predict accuracy of ____
test result; diagnosis
