Final exam
Epidemiology has been termed the 'basic science of Public Health'. The role of epidemiology in the health sciences covers all of the following except:
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In the process of establishing whether exposure to a certain risk factor is associated with unhealthy outcome, you expect distortions of accurate measure of the purported relationship to be hampered by?
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which of the following is NOT a reason for selecting the use of a case-control study design?
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key feature of the cross-sectional study design
-Measurements made at a single period of observation-Participants not chosen due to exposure or outcome-Measurements made on all participants-Main uses:-To study trends-To understand the characteristics of a population-To generate hypotheses of the relation between exposure and outcome
federal agencies that oversee human subjects research
NIH, FDA, department of education, department of energy,
surveillance systems of disease indicators
animal populations, environmental data, hazard surveillance in the workplace, drug/biological utilizations, student and employee data
limitations of longitudinal studies
feasibility, precision, long time
INTERMEDIATE genetic susceptibility
genetic configuration causes susceptibility
compliance
may be less in participants who believe they are not receiving the treatment, may be better in those who understand the principles on which the intervention is based,
survelliance system as information loops
multiple players, begins when disease is reported, doesn't end until information is related to those responsible for disease prevention
RR = 1
no association
endemic refers to
normal prevalence of disease in an area
analytic studies are two types
observational and experimental
ethic issues in epidemiology
obtaining consent, privacy, interpretation of risk, informing subjects of findings, objectivity of the researcher,
analytic approach to retrospective case control design
odds ratio
A specific case definition is one that
or tight case definition is one that is likely to include only (or mostly) true cases, but at the expense of excluding milder or atypical cases.
the case-fatality rate for a specific disease refers to
proportion of patients with a given disease who will die from that disease, and thus reflects the seriousness of the condition.
only direct method of measuring risk
prospective cohort study
you are interested in establishing whether intra-uterine adverse-health events results in adulthood diseases, what study design is most appropriate if you want to establish risk
prospective cohort study
goals of the IRB
protect subjects, promote public health good by supporting valid research
RR < 1
protective factor
disadvantages of retrospective case control design
recalled information, validation of exposure can be difficult, unable to control extraneous variables, may be difficult to find an aproppriate control,
analytic approach to prospective cohort studies
relative risk, risk ratio
tasks of the IRB
review all research, approve before it begins, review periodic reports, approve any changes to research, additional scrutiny for vulnerable populations
advantages of case studies
rich sources of hypotheses, unusual disease presentations are shared with the larger scientific commuunity
incidence density assumes
risk of outcome is constant for the entire duration fo the study, rate of disease is the same for dropouts as for those who continue under observation, disease lasts for at least 1 full unit of observation
lead time bias
screening detects disease earlier in its natural course which leads to false improvement in survival time
The incidence of colon cancer in a population may be decreased by
screening for prevention,
bias in longitudinal studies
selection, migration, missclassification, detection
Attributes of a Surveillance System
simplicity, felxibility, acceptabilitiy, sensitiivity, representativeness, timeliness, resource requirements
MOST genetic susceptibility
specific gene defect
prenatal genetic screening
specificity is key, most disorders are generally autosomal recessive
which of the following may occur during the incubation period
spread of disease without symptoms
disadvantages of cross-sectional studies
subclinical cases are missed, cannot measure risk, cannot make causal inferences, cannot test an hypothesis,
advantages of retrospective case control design
suited to rate disease, inexpensive, existing records can be used, no risk to subjects
purpose of genetic epidemiology
susceptibility or resistance to disease, and variates in response to treatment.
false negative
test result negative but disease present
false positive
test result positive but no disease
sensitivity
the ability of the test to identify correctly those persons tested who truly have the disease
specificity
the ability of the test to identify correctly those who do not have the disease
validitity
the extent to which a test measures or predicts what it is supposed to
true positive
the patient has the disease and the test is positive
analytic epidemiology
the study of risk factors and the relationships among risk factors for the purpose of understanding the etiology of the disease or condition
public health surveillance
the systematic collection, analysis, interpretation, and dissemination of health data describes and monitors health events, sets priorities, assists in planning public health interventions
volunteer bias
those with reason to worry are more likely to get screened, screening leads to higher number of cases
List three things that could lead to an increase in the prevalence of disease
treatment but no cure, less deaths, more detection, migration into an area
Years of Potential Life Lost is a particularly important concept for tracking the societal impact of pediatric diseases
true
a basic assumption of epidemiology is that disease occurrence is not random
true
herd immunity can protect all group members from certain infectious disease even though they all may not be immune
true
one way infectious disease can be transmitted is via FOMITE
true
incidence density assumes that following one person for ten years is equivalent to following ten people for one year
true?
limitations of the national notifiable disease reporting system
underreporting, lack of representativeness, lack of timeliness, inconsistency of case definition
the hallmark feature of an analytic epidemiologic study is:
use of an appropriate comparison group
screening test
used to seperate those who have a high probability of having the disease from a large group of apparently well persons, not intended to be diagnostic,
sources of data
vital statistics, morbidity data, outpatient health care data, surveys of health,
relative risk
what is my risk given that I have been exposed compared to those unexposed, incidence in exposed / incidence in unexposed
absolute risk
what is my risk jut by virture of being a member of the population, incidence in the population
odds ratio
what is the chance of developing the disease in exposed persons compared to the chance for disease in those not exposed
true negative
without disease and negative screening test
techniques to minimize bias in observational studies include?
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which of the following is a key assumption involved in the use of life-table analysis?
.Life-table analysis depends upon a consistent rate of survival during all periods of the study. Changes in the rate of survival may be due to external influences that are operating at later times on only a portion of the initial population. Since those who have died earlier in the study period will not experience these external influences, the comparison between periods is rendered invalid.
important concepts of genetic epidemiology
1. common disease are controlled by several genes 2. there are geographical disease differences because of genes and environment 3. genes for essential proteins tend to be conserved 4. variable genes have less clinical revelance
Wilson-Junger Criteria
1. condition should be an important health problem 2. accepted treatment for the disease 3. facilities for treatment should be available 4. recognizable latent or early symptomatic stage 5. suitable test for examination 6. acceptable test 7. condition should be understood 8. policy on whom to treat 9. cost of case finding should be balanced 10. case-finding should be a continual process
sequence of genetic studies
1. look for gene marker 2. explore nearby genes 3. establish functional association of genetic defect with disease
Kappa statistic
A measure of the degree of nonrandom agreement between observers of the same categorical variable.
kappa statistic
A measure of the degree of nonrandom agreement between observers of the same categorical variable.
common screening tests
BP, blood sugar, pap smear, cholesterol, mammography, PSA, occult blood for colon CA,
Describe the steps that the health department should take to investigate this outbreak
Early steps include confirming that the number of cases exceeds the expected number, verifying the diagnosis, and preparing for field work (which includes talking with laboratorians about specimen collection). Next steps include conducting surveillance to identify additional cases; analyzing the data by time, place, and person; generating hypotheses; and evaluating those hypotheses (for example, by conducting a case-control study)
Kaplan-Meier method
Estimates survival function: uses survival times to estimate the proportion of people who would survive a given length of time under the same circumstances, new interval with each event
types of genetic studies
HLA associations, linkage analysis
attributable risk
How much of the disease that occurs can be attributed to a certain exposure?
postive predictive value
Increase with prevalence of disease, probability the a positive is actually positve
medical surveillance
The monitoring of potentially exposed individuals to detect early symptoms of disease.
Standardized Mortality Ratio (SMR)
The observed number of deaths divided by the expected number of deaths and multiplied by 100. SMR is regarded as a measure of the relative risk of the studied group to die of a particular condition
negative predictive value
The probability that a person with a negative test result is truly disease free refers to what value?
case study characteristics
a single event, series of events is described, often unusual or noteworthy because of temporal or spatial clustering
hurdles in the study of chronic diseases
absence of an agent, multifactoral etiology, long latency, indefinite onset
the number of deaths from lung cancer during 2005 in persons 40-49 years divided by the 2005 midpoints population of persons 40-49 years old is defined as:
age specific mortality rate
the epidemiologic triangle is best described as
agent, host, environment
active surveillance
better data, expensive, specific disease, limited period of time
can establish causality
clinical trial
intent to treat analysis
compares the outcome of interest between the study groups based on the treatment to which why were randomized regardless of whether the individuals actually took their assigned treatment or not
strengths of longitudinal studies
correct temporal relationship, disease rates obtained directly, can evaluate rare exposures, can evaluate multiple outcomes from a single exposure, generally good exposure informaiton
statistical approach to cross sectional studies
correlation
advantages of cross sectional studies
data can be collected consistently for an entire population, can determine the magnitude of the problem, can identify possible causes, inexpensive, useful to assess health status and healthcare needs of a population
purpose of cross-sectional studies
describe distribution of disease its associated risk factors at one point in time, a "snapshot" of the experience of a defined population at a given time or ate a specified point in life
in a retrospective cohort study, the main difference from the prospective cohort study is?
disease is identified first then looks for exposure where prospective starts with exposure
participation of screening decreases with
disease phobia, stigma, unpleasant treatements, socioeconomic status, lack of access
LEAST genetic susceptiblity
external factors only
reporting is an obligation of
health professionals, medical examiners, administrators of health facilities and schools, lab directors
the ability of a single person to remain free of clinical illness following exposure to an infectious agent is known as
immunity
if we wish to measure risk in the population then we should look at the:
incidence
RR > 1
increased risk
a good surveillance report can serve to
inform and motivate
disadvantages of case studies
inherently biased, cannot test an hypothesis, no time dimension, no comparison group
retrospective case control design
investigates an association of a prior exposure to disease by determining is the exposure was more frequent among diseased cases, exposure is recollected after the development of disease
when an infectious disease outbreak occurs, investigators usually construct an 'epidemic curve'. This is because:
it can help identify type of outbreak and incubation periods
state health department requires reporting of a disease if
it causes serious disease or death, has potential to affect additional people, can be controlled or prevented, outbreaks with high incidence must be reported, and occurence of an unusal disease
John Snow's investigation of cholera is considered a model for epidemiological field investigations because it included a:
it included a biologically plausible (but not popular at the time) hypothesis that cholera was water-borne, a spot map, a comparison of a health outcome (death) among exposed and unexposed groups, and a recommendation for public health action. Snow's elegant work predated multivariate analysis by 100 years.
participation in screening increases with
knowledge of condition, perception of surceptiiblity, knowledge of treatment
incomplete reporting is caused by
lack of knowledge of what is reportable, lack of knowledge how to report, perception that it is not important
length time bias
less agressive disease allows time for screening leads to false benefit of screening