HLTH 444 Exam 3
-Case Control: Analytic, observational study that compares 2 groups of
people who do or do not have a disease (cases are those who have disease
and controls are those who do not)
-Prospective Cohort (Longitudinal): Subjects are classified according to
their exposure to a factor of interest and then are observed over time to
document the occurrence of new cases (incidence) of disease or other health
events
-Retrospective Cohort: Uses historical data to determine exposure level in
past
-Cross-sectional- A study in which a representative cross section of the
population is tested or surveyed at one specific time.
●Describe advantages and disadvantages of case-control and cohort
studies
-Advantages (Cohort): Permit direct observation of risk, Exposure factor is
well defined, Can study exposures that are uncommon in population,
Temporal relationship between factor and outcome is known
-Disadvantages(Cohort): Expensive and time consuming (especially for rare
diseases with long latency), Complicated and difficult to carry out, Subjects
may be lost to follow-up during study, Exposures can be misclassified.
-Advantages (Case-control): used to study low-prevalence conditions,
Having a disease is a criterion for being selected as a case, quick and easy to
complete, Usually inexpensive, Involve smaller number of subjects
-Disadvantages (Case-control):Measurement of exposure may be
inaccurate, Representativeness of cases and controls may be unknown,
Provide indirect estimates of risk, The temporal relationship between
exposure factor and outcome cannot always be ascertained.
●Define odds ratio, relative risk, and population risk difference
-Odds Ratio: Measure of association between frequency of exposure and
frequency of outcome used in case-control studies (OR = AD/BC)
-Relative Risk: Ratio of the incidence rate of a disease or
health outcome in an exposed group to the incidence rate of
the disease or condition in a non exposed group (RR) = [A/(A + B)] ÷ [C/(C + D)]
-Population Risk Difference: Incidence in total population – incidence in
nonexposed segment
●Identify components and uses for randomized controlled trials
-Randomized control trial: clinical-epidemiological experiment in which
subjects are randomly allocated into groups, usually called test and control
groups, to receive or not to receive a preventive or a therapeutic procedure
or intervention
-Study sample: Rigorous inclusion and exclusion criteria
-single-blind: Researcher knows, participant does not
-double blind: Both don’t know
-cross-over studies: Participants may be switched between treatment
groups
●Distinguish between:
-experimental studies: Implemented as intervention studies
–Investigator
–Controls who is exposed to factor of interest
—Assigns subjects randomly to study groups
-quasi-experimental studies: Investigator manipulates the study
factor but does not assign individual subjects randomly to exposed and
nonexposed groups
●Identify components, key people and groups involved in the policy
cycle
-Policy cycle comprises several stages:
1. Problem definition, formulation, and reformulation
2. Agenda setting: Setting priorities, deciding at what time to deal with a public
health problem or issue, and determining who will deal with the problem
3. Policy establishment (i.e., adoption and legislation),
4. Policy implementation,
-5. Policy assessment: Final stage in policy cycle; refers to determination of whether
the policy has met defined objectives and related goal
(Epidemiologists provide contributions to each of these stages)
-Policy Actors: Individuals who are involved in policy formulation
Include members of legislature, citizens, lobbyists, and representatives of advocacy groups
-Stakeholders: Individuals, organizations, and members of government who
are affected by policy decisions
-Legitimization:
Process of making policies legitimate, meaning to be acceptable to norms of society
-Interest Group: Non-profit and usually voluntary organization whose
members have a common cause for which they seek to influence public policy,
without seeking political control
●Identify terms such as:
-hazard identification: examines the evidence that associates
exposure to an agent with its toxicity and produces a qualitative judgment
about the strength of that evidence, whether it is derived from human
epidemiology or extrapolated from laboratory animal data”
- risk assessment: a process for identifying adverse consequences
and their associated probability.”
- exposure assessment: identifies populations exposed to the
toxicant, describes their composition and size, and examines the roots,
magnitudes, frequencies, and durations of such exposures
- dose-response assessment: Measurement of the relationship
between the amount of exposure and the occurrence of the unwanted
health effects
●distinguish between sensitivity and specificity, predictive positive and
negative values
-Sensitivity: Ability of test to identify correctly all screened individuals who
actually have the disease
-Specificity: Ability of test to correctly identify individuals who actually do
NOT have the disease
(Needs to be at least 90% to be accepted)
-Positive: The proportion of individuals screened positive by the test who
actually have the disease
-Negative: Analogous measure for those screened negative by the test
●Identify components of a screening test according to Gold Standard
-Determines Validity
-Definitive diagnosis that has been determined by biopsy,
surgery, autopsy, or other method
-Provides standard against which sensitivity (and specificity) are evaluated
●Define such terms as risk and hazard
-Risk:s "...estimates of the number of excess unwarranted health events
expected at different time intervals at each level of exposure".
-Hazard:inherent capability of an agent or a situation to have an adverse
effect. A factor or exposure that may adversely affect health.
●Be aware of ethics guidelines for research and the example of the
Tuskegee Study
-Syphilis investigation from 1932 to 1972, Purpose was to “...record the
natural history of syphilis in hopes of justifying treatment programs for
blacks...”
-A total of 600 African American men participated.
-399 syphilis cases and 201 syphilis-free controls, Never gave informed
consent
-Despite discovery of penicillin, men were never offered treatment.
-Class-action suit filed in 1973
●Identify the natural history of disease and associated levels of
prevention
-Natural History: Time course of disease from beginning to final clinical
endpoints
-Prepathogenesis: Time period in natural history of disease before disease
agent (e.g., bacterium) has interacted with host (person who develops
disease) or prior to disease process starting (e.g., abnormal cell division in
cancer)
-Pathogenesis:
After agent has interacted with host or disease process has
started for noninfectious diseases
-Prevention: Three levels coincide with periods of prepathogenesis and
pathogenesis.
-Primary: Prepathogenesis period (Immunization, sunscreen, Healthy eating)
-Secondary: Early pathogenesis period, prior to signs and symptoms (Screening)
-Tertiary: Late pathogenesis period, after signs and symptoms develop
(Therapy after stroke, insulin for diabetes)
●Identify key screening tests for newborns and key screening test for
adults
-Newborns: Hearing deficits, Heart defects
-Blood screening tests (Phenylketonuria (PKU), Sickle cell disease (SCD)
-Adults: Cancer screening, Diabetes, Cholesterol,Human immunodeficiency virus (HIV),
Genetic screening, Depression
●Identify components of an ecological study
-study in which the units of analysis are populations or
groups of people rather than individuals
-Examples of groups: nations, states, census tracts, counties
-May be used when individual measurements are not available,
but group-level data can be obtained
-Ecologic comparison study: An assessment of the association between
exposure rates and disease rates during the same time period
-Ecologic correlation: An association between two variables (exposure and
outcome) measured at the group level
-Ecologic (Ecological) Fallacy: "An erroneous inference that may occur
because an association observed between variables on an aggregate level does
not necessarily represent or reflect the association that exists at an individual
level;...
●Distinguish attributable risk
-in a cohort study, Refers to the difference between the incidence rate of a
disease in the exposed group and the incidence rate in the nonexposed group.
-From previous example: Attributable risk per thousand:[(3/107) × 1,000] –
[(2/603) × 1,000] = 28.03 – 3.32 = 24.71 per 1,000
●Identify major bias in studies that impact validity
-Lead-time bias makes it falsely appear that survival has improved with
screening
-Length bias refers to screening preferentially finding slow growing, less
aggressive forms of disease
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