Evidence -Based Approaches to Public Health: Concepts of Epidemiology Flashcards
Ratio
Dividing one number by another, but the numerator does NOT need to be a subset of the denominator. 2 different quantities
Proportion
Dividing one number by another, but the numerator DOES need to be a subset of the denominator
Rate
Dividing one number by another but adding a time component in the denominator
Incidence
Measure of the number of new cases of a disease
Cumulative Incidence
Number of new cases of a disease in a period of time
Incidence Rate
Number of new cases of the disease during person-time of observation
Prevalence
Number of existing cases of a disease during a given time period. May include new cases as well
Point Prevalence
The proportion of the population that is diseased at a single point in time
Period Prevalence
The proportion of the population that is diseased during a specific duration of time
Endemic
A situation in a community in which there is a consistent elevated rate of a certain disease
Epidemic
An increase in the number of cases in a community, above what is expected
Pandemic
Worldwide epidemic
Descriptive Studies
Generally observational (no hypothesis testing)
- case reports
- case series
- cross-sectional
Analytical Studies
Interventional (experimental) and observational (hypothesis testing)
- Experimental
- RCT
- Non-Randomized Control Trial
- Observational
- Cohort
- Case-Control
- Cross-Sectional
Case Studies/Case Reports
Studies are used to alert people of a new illness or new association with illness. Reports of only people with the condition of interest.
Cross-Sectional Studies
Studies that include people who are representative of a given population. Not selected based on illness or exposure and can be used to determine initial association and identify the prevalence of either exposure or illness in a group.
Ecological Studies
Studies that are used to describe populations. Not analyzed on an individual level.
Ecological Fallacy
Group level data are used to report on individuals
Case-Control Studies
Studies select people with or without disease and then proceed to look back over time to see if people had different rates of exposure. Good for rare diseases with long latency periods
Latency Period
Diseases that take a long time to develop
Cohort Studies
Studies that selected people on the basis of exposure and determine if people develop the disease at different rates. Good for rare exposures and may follow individuals into prospective or retrospective. Incidence can be calculated from this type of study. Prevalence cases are excluded
Prospective
Into the future
Retrospective
Looking back in time
Prevalence Cases
People who have the disease at the time point when the study period begins
Randomized Control Trial (RCT)
Tests an intervention that is given by the researcher by 2 or more groups. People are randomly assigned into groups through randomization with one given the active item and the other group the usual treatment or a placebo. The researcher follows them over time and compares outcomes. Participants do not know which group they are in.
Systematic Review and Meta-Analyses
Pool the results of multiple independent studies with established criteria to identify the evidence for associations
Relative Risk
Measure of the magnitude of an association between an exposure and a disease that is used in cohort studies. Ratio of the risk (incidence) of disease exposed to the risk in the nonexposed
Odds Ratio
Calculated in case-control studies or cross-sectional studies. Odds of exposure among cases divided by odds of exposure among controls, which equals the odds of disease among the exposed divided by the odds of disease among the nonexposed.
RR or OR = 1
No association between exposure and outcome
RR or OR > 1
Exposure increases the risk of the outcome
RR or OR < 1
Exposure decreases the risk of the outcome
Bias
A systematic error as compared to an error attributable to chance alone
Selection Bias
Results from procedures used to select participants for a study. Occurs in a case-control or retrospective cohort study. This may also happen in a prospective cohort study and experimental studies
Observation Bias
Arises from systematic differences in the way information on exposure or disease is obtained from the study groups
Recall Bias
Inaccurate reporting of past events
Interviewer Bias
Effects of the interviewer’s body language, voice, or demeanor on the response
Misclassification Errror
Participants were classified into the wrong population.
- Differential (bias different between groups)
- Non differential (bias is equal across groups)
Confounding
A third variable distorts the findings and is associated with both the exposure and outcome. Distorts the true association
Effect Modification
The magnitude of the association between an exposure and outcome varies by the presence or level of a third variable. Clarifies the association
Stratification
Divides the data according to the levels of the variable and allows the calculation of a measure of association for each strata
Crude
Overall
Koch’s Postulates
- Microorganisms must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
- It should be possible to isolate the causative microorganism from a diseased organism and grow it in pure culture.
- The organism from pure culture should be able to cause disease when inoculated into a healthy host organism.
- The microorganism should then be able to be isolated from the new host and grown in pure culture.
Helped identify causation
Hills Nine Criteria of Causality (1965)
- Analogy
- Coherence
- Reversibility
- Specificity
- Plausibility
- Strength of the Association
- Consistency
- Biological Gradient
- Temporality
Primordial Prevention
The earliest stage of prevention. Preventing risk factors of disease by targeting lifestyles, behaviors, and exposure patterns at the aggregate level instead of the individual level in order to decrease the risk of disease
Primary Prevention
Concerned with preventing disease. Takes place before biological onset of disease
Secondary Prevention
Prevention is addressed by most screening programs. Occurs in the preclinical phase after the disease is present but before symptoms appear.
Tertiary Prevention
Focused on rehabilitation and support. The disease has occurred, and the goal is to improve the quality of life and reduce symptoms.
Feasibility
How likely the target audience is to participate in a recommended program
Reliability
Repeatability
Validity
The ability of a test to accurately identify diseased and nondiseased individuals
Sensitivity
The ability of a test to correctly identify the number of people WITH the disease
True Positives
Individuals who have the disease and test positive for the disease
False Negatives
Individuals who have the disease and test negative for the disease
Specificity
The ability of a test to correctly identify the number of people WITHOUT the disease
True Negatives
Individuals who do truly do not have the disease and test negative
False Positives
Individuals who do truly do not have the disease and test positive
Positive Predictive Value
Number of people who test positive who actually have the disease divided by the number of positive tests
Negative Predictive Value
Number of people who test negative for disease and do not have the disease divided by the number of people who tested negative
Gold Standard
A definite diagnosis that has been determined by biopsy, surgery, autopsy, or another method
Cutoff Value too Low
Sensitivity is high and specificity is low
Cutoff Value too High
Sensitivity is low and specificity is high
Receiver Operating Characteristic Curve
Used to set the cutoff value of a continuous value test
Lead Time Bias
Overestimation of survival duration attributable to earlier detection by screening than by clinical presentation
Length Bias
Screening is more likely to detect cases that are progressing slowly compared with those with rapid progression of diseases, that manifest clinically. Overestimation of survival
Statistical Signifance
Whether the calculated estimate is likely to be observed assuming the null hypothesis is true
Practical/Clinical Significance
Subjective Assessment of whether the effect estimated in a test is “important” or “meaningful”. Not summarized in a specific measure. Based on researchers knowledge of the environment and judgement as to whether the estimated effect is meaningful
Social Determinants of Health
Factors in a social environment that contribute to or detract from the health of individuals and communities. Ex. socioeconomic status, transportation, housing, access to services, discrimination by social grouping, and social or environmental stressors.
Surveillance
Systematic ongoing collection, analysis, interpretation, and dissemination of health data. Ex. diseases, birth and death certificates, disease registries
Active Surveillance
The research team goes out into the community and looks for cases of the disease. Accurate but expensive
Passive Surveillance
Relies on existing reporting systems
Digital Surveillance
Refers to web crawling to identify reports of disease.
Sentinel Surveillance
Monitors a special community to look for changes in the distribution of disease. Conducted in a small location.