Module 13 Flashcards
what does clinical epidemiology focus on?
- the application of epidemiologic methods to assess the efficacy of screening, diagnosis, and treatment in clinical setting
- use to ID the health consequences of employing a test or administering a treatment
what is health screening used to evaluate?
to evaluate people without signs or symptoms of disease to ID people who may have the disease
why do we do screening?
Screening is used to promote detection of diseases in their earliest stages, when treatment has the greatest chance of working, in order to reduce morbidity and mortality
what level of prevention is screening?
- secondary prevention
- health screening activities are used to ID disease during the preclinical (subclinical, presymptomatic, latent) stage of disease
stage of subclinical disease
- Not apparent or asymptomatic
- Pathological changes occur and some can be detected by screening
- Incubation period for infectious diseases
- Latency for chronic disease
Screening and Levels of Prevention: primary
- Primary = Prevention of disease
- Proper nutrition
- Immunization
- Proper sanitation
- Hand washing
Screening and Levels of Prevention: secondary
- Secondary = Detection of disease
- Early cancer screening
- Bone density scans
- Cholesterol testing
- Hgb A1C testing
what is mass screening?
- Involves application of screening tests to the total population
- Not a selective process
what is selective screening?
- Involves applying the screening tests to high risk
groups - Selective process
Screening vs. Diagnosis
- Screening is not the same as making a diagnosis
- Screening identifies people who are likely to have the disease
- When a person has a positive screening test, additional testing is needed to make a diagnosis
- Screening and diagnosis are a 2-step process:
- Screening is used to identify people who are likely to have the disease
- People with a positive screening test need to undergo additional testing to confirm the presence of the disease
Screening Tests:
What They Cannot Do
- Screening tests are not diagnostic
- Screening tests are not able to perfectly identify everyone with the disease
- Screening tests may not be able to identify people who will develop the disease in the future
what are the measures used to evaluate screening tests?
- Sensitivity
- Specificity
- Positive Predictive Value
- Negative Predictive Value
sensitivity
- Probability that a person with the disease will test positive for the disease (true positive)
- The ability of the test to correctly identify those with the disease
- Probability of correctly identifying the disease
- Very good at identifying the diseased patient
- Has a low percentage of false negatives
- Very important if a disease is fatal, contagious, or early treatment helps
specificity
- Probability that a person who does not have the disease will test negative for the disease (true negative)
- The ability of the test to correctly identify those without the disease (those who tested negative are the true negative)
- Very good at identifying the patients without a disease
- Has a low percentage of false positives
Positive Predictive Value
- Probability that a person who has a positive test actually has the disease
- Proportion of people with a positive test result who have the disease
- Prevalence influences the PPV
- When you are looking for a disease that is very rare, a positive screening test result is more likely to be a false positive than a positive test result in a population where a large percentage of the population has the disease
Negative Predictive Value
- Probability that a person who has a negative test does not have the disease
- Proportion of people with a negative test result who do not have the disease
**as prevalence increases, the positive predictive values also increases, but negative predictive values decreases
what does the epidemiologic triad for infectious disease include?
- environment: surrounding and conditions external to the human or animals that cause or allow the disease transmission
- time: duration of exposure
- host: human or animal that is susceptible to the disease (e.g. healthcare workers who are in high risk setting)
- agent: the cause of the disease
Epidemiologic Triad for
Communicable Diseases
- Shows the interaction and interdependence of agent, host, environment, and time as used in the investigation of diseases and epidemics
- An epidemic can be stopped when one of the elements of the triangle is interfered with, altered, changed, or removed from existence, so that the disease no longer continues along its mode of transmission and routes of infection
what is in the chain of infection?
- Reservoir (environment, human, animal, etc)
- Portal of exit (nose, mouth, rectum, bodily fluid)
- Transmission
- Direct
- Indirect
- Airborne
- Portal of entry (mucous membrane, non-intact wounds, etc)
- Susceptible host
breaking the chain of infection
- Eliminate or sanitize the reservoir
- Eliminate, cover, or filter the portal of exit
- Eliminate or sanitize the transmission mode
- Cover or filter the portal of entry
- Immunize the host and place the host in good health
**for direct transmission –>think about person to person
**for indirect transmission think about vectors (mosquitoes) and the vehicle of transmission to stop the indirect mode of transmission such as infected water, food, etc
what is active immunity?
- Body produces its own antibodies in response to
having been vaccinated or having a specific disease pathogen invade the body
what is passive immunity
- Administration of immune globulin
- Transplacental transfer of maternal immune globulins to the fetus during pregnancy
- Transfer of antibodies and other immunoprotectants in mother’s milk during breastfeeding or feeding of pumped milk
Herd Immunity
- Viewed as the resistance a population has to the
invasion and spread of an infectious disease - Based on the notion that if a population or group
is mostly protected from a disease by immunizations (85% or more, depending on the disease), then the chance of a major epidemic
occurring is highly limited
Host-Related Control and Prevention: isolation
- Used for persons who are known to be ill with a contagious disease.
- Used in inpatient settings (hospitals or nursing homes)
- State laws as well as accrediting organizations require one or two beds to be designated and as isolation beds
Host-Related Control and Prevention:Quarantine
- Used for persons who have been exposed to a contagious disease but may or may not become ill
define: case
- An individual who has the disease, disorder, injury, health behavior, or health event of interest
define: primary case
- First case of the disease or condition or behavior
define: index case
- First case brought to the epidemiologist’s attention
(not necessarily the primary case)
define: secondary cases
- Cases that became ill after the disease was introduced into the population and become infected from the primary case
define suspect case
- An individual who has all of the signs and symptoms of a disease or condition, yet not diagnosed
what is endemic
Amount of disease usually present in a community
what is hyperendemic
- Persistent high levels of disease
what is sporadic?
- Occurs infrequently and irregularly
*seen occasionally and w/o geograpically concentration
what epidemic?
- An increase in the number of cases above what is expected in the population in that area
what is outbreak
- An epidemic but in a limited geographic area
what is pandemic
Epidemic that has spread over several countries or
continents
Spread of Epidemics: common source
- Attributed to a specific source
- Point sources (person is exposed in a brief period, everyone who becomes ill does so in one incubation period and there is one common source)
- Intermittent sources (occurs when there’s an intermittent exposure)
- Continuous sources (occurs when there’s a continuous exposure to the common source)
Spread of Epidemics: propagated
- Transmitted from person to person (via direct or indirect or vegetable tranmission)
- Lockdown effect in waves?
Spread of Epidemics: mixed epidemic
- Starts with a common source
- Then spread by person-to-person contact
**common source and propagated type
What is Field Epidemiology?
- Field epidemiology has been defined as the application of epidemiology under a set of general conditions
- The problem is unexpected
- A timely response may be needed
- Travel to and work in the field is required by epidemiologists to solve the problem
- The investigation time is likely to be limited because of the need for timely intervention
field investigation
Field investigations involving acute problems may differ from conventional epidemiologic studies in three important ways:
1. Field investigations often do not start with a clear hypothesis
2. Acute problems involve an immediate need to protect the public and resolve the concern
3. Field epidemiologists must decide when the available information is sufficient to take appropriate action
Conceptual definition
- Defines the concept
- Dictionary definition
Operational definition
- Describes the operations used to measure the
variable of interest including the - Procedures
- Instruments
