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