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Epidemiology
Epi Block 1
113
Medical
Graduate
10/24/2009

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Cards

Term
Disease
Definition
a physiological dysfunction
Term
Illness
Definition
subjective state of the person who feels aware of not being well
Term
Sickness
Definition
state of social dysfunction
Term
Epidemiological triad
Definition
Person, place, time is part of what?
Term

  • age
  • sex
  • race/ethnicity

Definition

 

3 aspects of "Person" of the epidemiologic triad

 

Term

 

  • geographic location
  • proximity to exposure
  • clustering

 

Definition

 

3 aspects of "Place" of the epidemiologic triad

 

Term

 

  • date/time of exposure
  • Seasonality of infection
  • identifying endemic versus epidemic disease rates

 

 

Definition
3 aspects of "Time" of the epidemiologic triad
Term
Endemic
Definition
Habitual presence of a disease among population of given geographic area
Term
Epidemic
Definition
Occurrence of group of illness similar in nature within a given geographic region in excess of normal expectancy
Term
Pandemic
Definition
Worldwide Epidemic
Term
Herd Immnuity
Definition
Resistance of a group to an attack by a disease to which are large portion of members of the group are immune
Term
Virulence
Definition
Severity of the disease produced by an organism
Term
Virulence
Definition
# of cases of overt infection/# of total infections
Term
Infectivity
Definition
Capacity of an agent to enter and multiply in a susceptible host
Term
Pathogenicity
Definition
Capacity of an agent to cause clinical symptoms
Term
Toxigenicity
Definition
Capacity of an agent to produce toxins
Term
Antigenicity
Definition
Ability of an agent to induce antibody production in host
Term
Direct Transmission
Definition
Person to person contact
Term
Indirect transmission
Definition
Common vehicle or vector is what type of transmission?
Term
Latent period
Definition
Time interval from infection to development of infectiousness
Term
Infectious period
Definition
Time during which the host can infect another host
Term
Symptomatic period
Definition
Time during which symptoms present
Term

 

  1. Increased in amount of virulence
  2. Recent intro of agent into a new setting
  3. Enhanced mode of transmission
  4. Factors that increase host exposure or involve introduction through new portals

 

Definition
4 reasons why outbreaks occur
Term

  1. a case may be a source
  2. some people may be immune
  3. there's sometimes a need for urgency
  4. preventative measures have a clear scientific basis

Definition
Four unique features of infectious disease
Term
Counts
Definition
# of cases being studied with disease is referred to as what?
Term
Ratio
Definition
relationship between two numbers (no relation of the the two numbers)
Term
Proportion
Definition

  • A ratio where the numerator is included in the denominator
  • Tells us what fraction of the population is affected
  • Ex. males/total population

Term
Rate
Definition

 

The following are seen in what formula?
  • a defined time interval
  • # of events occurring in that time interval
  • population at risk in that time interval
  • a multiplier or constant (x10, X100, etc)

 

Term
Incidence
Definition
Measures risk of developing a new disease within a specific time period
Term
Cumulative Incidence (Incidence proportion)
Definition

# of new events during a given time period/

population at risk during this time period

 

x100

Term
Attack rate
Definition

 

  • Cumulative incidence calculated for a specific disease for a limited time period during an epidemic
  • Usually in relation to food-borne ilnesses
  • measured from beginning of outbreak to end of outbreak

 

Term
Attack Rate
Definition
# of exposed persons with a disease/# of total exposed persons
Term
Prevalence
Definition

# of existing events, old and new/population at risk 

 

x1000

Term
Point prevalence
Definition

 

  • measures the frequency of all existing events at a given instant of time
  • ex: existing cases on 9/16/1979

 

Term
Period Prevalence
Definition

 

  • measures frequency of existing cases for a prescribed period of time
  • ex: existing cases in 1975

 

Term
Risk
Definition

 

  • probability statement during given period of time
  • ex: 1 in a million chance of developing cancer in 70 years

 

Term
Rates
Definition
Can be used to estimate risk if the time period is short (annual) and the incidence (new cases) of disease over the interval is relatively constant
Term
Cumulative Incidence
Definition
Produces an estimate of the probable risk that an individual will develop a disease during a specific period of time
Term
Competing Risks
Definition
The phenomenon of being removed from a study through death or from other causes is referred to as what?
Term
Incidence Density
Definition

# of new cases of disease during period

 

/

 

total "person time" of observation

Term
Person-Time
Definition
Each subject contributes a specific time of observation (days, months, years) to the denominator of the incidence density equation is known as what?
Term
Screening Tests
Definition
This test does not formally diagnose illness
Term
To lower the morbidity and mortality of the disease in a population (control rather than eliminate the disease)
Definition
What is the screening objective
Term

  • early detection leads to more favorable prognosis
  • pre cinical-disease left untreated progresses to clinically evident disease
  • disease should be serious
  • prevalence of pre-clinical disease should be relatively high among those screened

Definition
What are 4 requirements for screening?
Term

 

  1. financial
  2. anxiety
  3. some morbidity occurs
  4. creation of lead time morbidity (lead-time- the time by which screening advances diagnosis)

 

Definition
What are 4 "costs" of screening
Term
Screening
Definition
Detection test to people who are yet asymptomatic.
Term
Total Pre-clinical Phase
Definition
Begins at initiation of disease (exposure) and ends when the disease is clinically manifested
Term
Detectable pre-clinical Phase
Definition
Begins when screening test is able to detect disease and ends when disease is clinically evident
Term
Validity
Definition
This is known as the extent to which the test distinguishes between persons with and without the disease
Term
High Validity
Definition

 

The following are requirements of what?
  1. High sensitivity
  2. High specificity
  3. Reliability
  4. Low cost minimally invasive
  5. Performance
Term

Sensitivity

 

Definition
This test classifies a diseased person as likely to have the condition (true positives)
Term
Specificity
Definition
This test classifies a non-disease person as unlikely to have the condition (true negatives)
Term
a/a+c
Definition
Sensitivity equation
Term
d/b+d
Definition
Specificity equation
Term
To have high sensitivity and high specificity but this is often not possible
Definition
What is the goal of screening tests
Term
Run an experimental design
Definition
How do you draw a cause an effect conclusion
Term
Experimental Studies
Definition

The following are three key features of what type of studies?

  1. manipulation of independent variable
  2. control condition
  3. random assignment of participants to groups

Term
Casual interference (conclusion where one event or variable causes another
Definition
Experimental design is considered the "crown jewel" of designs b/c if done properly it allows what?
Term

Extraneous variable

 

 

example:  drinking coffee causes CVD

an extraneous variable could involve smoking

 

Definition

What can influence the dependent variable that researchers are unaware of in an experimental study? 

 

 

Term
Random Assignment
Definition
Each participant has an equal chance of being selected to experimental or control condition
Term
Attrition
Definition
Refers to a loss of participants during the course of an experimental study
Term
Differential Attrition
Definition
Situation when participants are leaving one independent condition at a higher rate than another
Term
Participation Bias (Demand characteristics)
Definition

  • Cues in an experiment that may lead a participant to respond in a particular fashion

Term
Good participant effect
Definition
Participant may behave the way they perceive the experimenter want them to
Term
Experimenter Bias (Rosenthal effect)
Definition
Experimenter knows how participants are expected to respond and may unwillingly coach them to respond in particular way
Term
Double Blind Study
Definition
What is the best way to deal with experimenter and participant bias?
Term

 

  • Type of people that may participate in the trial
  • schedule of tests, procedure, medicaitons, and dosages
  • length of the study

 

Definition
What 3 things does protocol describe?
Term
Primary outcome
Definition

Main efficacy variable being studied

ex: lower BP, better controlled DM, absence of sx

Term
Secondary outcome
Definition

Additional variables thought to be important

ex: quality of life, return of normal function, patient satisfaction

Term
Phase I
Definition

What phase of clinical trial involves

 

  • Researchers test an experimental drug or tx on a small group of people (10-30)
  • first time to be evaluated
  • determines safety, safe dosage and range, and identifies side effects

 

Term
Phase II
Definition

What phase of clinical trials involve

 

  • experimental study drug or tx given to a larger number of people (100-300)
  • sees if it is effective and further evaluates it's safety

 

Term
Phase III
Definition

What phase of clinical trials involves

 

  • experimental drug or tx given to a large group of people (1,000 - 3,000)
  • confirms effectiveness, monitors side effects, compares it to commonly used tx, and collects info that will allow the experimental drug or tx to be used safely

 

Term
Phase IV
Definition

What phase of clinical trials involves

 

  • Post- marketing studies to delineate additional information including the drug risks, benefits, and optimal use

 

Term
Informed Consent
Definition
This is not a contract and participants may withdraw from clinical trials at any time
Term
Double-blind crossover study
Definition

  • Participants receive real treatment or placebo and then are switched to opposite treatment
  • This trial doubles the number of people in the trial

Term
Observational Study
Definition
Investigator takes advantage of natural events and studies them
Term
Interventional Study
Definition

 

  • Clinical trial
  • the investigaor determines who gets the exposure and who does not

 

Term
Chance Associations
Definition
A non-casual expectation that occurs at random
Term
Artifactual Associations
Definition
A non-casual explanation that occurs through some error or defect in design or execution of study
Term
Indirect Associations
Definition
Exposure is associated with an outcome but through a third factor or variable (telephone and CHD)
Term
Descriptive Epidemiological Studies
Definition

 

  • Studies that make an attempt to describe patterns of disease and antecedent factors as they occur in "free-range" human population
  • Often provide first clues as to the relationship between exposure and outcomes
  • Ex: fluoride and dental care, or smoking and lung CA

 

Term
Case reports
Definition
Type of descriptive study that suggests expousre preceded by outcome but no proof
Term
Cross-sectional 
Definition
Type of descriptive study that is not clear which is exposure and which is outcome
Term
Ecological
Definition

 

  • Type of descriptive study that provide population wide estimates of disease rates vs exposure
  • Data often compares countries across the world
  • Ex; dietary fat intake by countries and breast cancer

 

Term
Descriptive Studies
Definition
What type of studies lead to a hypothesis but does not provide definite answers?
Term

  • Case reports
  • Cross-sectional
  • Ecological

Definition
What are 3 types of descriptive studies?
Term

  1. Cohort Studies (prospective and retrospective)
  2. Case-Control studies

Definition
Two types of analytic studies
Term
Retrospective study
Definition

  • In this type of cohort study, exposure and outcome have already occurred
  • Subjects have a disease

 

Term
Prospective Study
Definition

 

  • In this type of cohort study, outcome has yet to occur
  • Subjects are disease free

 

Term
Prospective Study
Definition
Relative Risk is a ratio in what study
Term
Retrospective Study
Definition
Odds ratio is a ratio in what type of study?
Term
Retrospective 
Definition

The following are advantages of what type of cohort study:

  • cost (follow up is not required)
  • Time (uses data from records)
  • rare outcomes (studies rare outcomes by going through records)

Term
Retrospective
Definition
Memory recall and bias are disadvantages of what type of cohort study
Term
Case-Control
Definition

 

  • What type of analytic study begins with the outcome and proceed to look back at the hx of exposure

 

Term

odds for exposure among cases/odds for exposure among controls

 

       a/c

OR= ______

 

       b/d

Definition
What is the formula for Odds Ratio
Term

 

  • controls should come from same source as cases
  • prevalence of exposure of controls should reflect prevalence of exposure of cases
  • time during which a subject is eligible to be a control should be the time in which an individual is also eligible to be a case

  • If all are not met you will have selection bias

     

    Definition

    What are 3 ways you select controls for case-control studies?  And if all three ways are not met what will you have?

     

     

    Term

     

    1. General population
    2. Random digit dialing
    3. Neighborhood
    4. Friends/Relatives
    5. Hospital/clinic-based

     

    Definition
    What are 5 sources of controls?
    Term

    optimal 1:1

    should not exceed 1:4

    Definition

    What is the optimal case-control ratio?

    What should the ratio not exceed?

    Term

    1. Self report
    2. Records
    3. Interviews with surrogates (spouses, children)

    Definition
    What are 3 sources of exposure data?
    Term
    Nested Case Control
    Definition

    A hybrid design in which a case-control study is within a cohort study

     

    cases------COHORT STUDY----controls

    Term
    Exposure data is collected before disease development eliminating recall bias
    Definition
    What is an advantage of a Nested Control Study
    Term

     

    • quick and inexpensive
    • well suited for evaluation of disease with long induction periods
    • optimal for evaluation of rare diseases
    • can examine multiple etiologic factors for a single disease

     

    Definition
    What are some advantages of a case-control
    Term

     

    • inefficient for evaluation of rare exposures
    • difficult to establish the temporal relationship between exposure and disease
    • prone to bias

     

    Definition
    What are some disadvantages of case-control studies?
    Term
    Prospective Study
    Definition

     

    • Disease free individuals are selected and their exposure status is ascertained
    • Subjects are followed for a period of time to record and compare the incidence of disease between exposed and non-exposed (Risk ratio)

     

    Term
    Prospective Study
    Definition

     

    • This is the strongest observational study
    • Examines multiple effects/outcomes
    • Yields info on multiple exposures
    • Allows direct measurement of incidence of disease in exposed and non-exposed group

     

     

    Term
    Prospective Study
    Definition

     

    • This study is not efficient study for rare diseases
    • is costly and time consuming
    • requires a large sample size
    • changes over time in diagnostic methods can lead to bias

     

    Term
    Case-Control Study
    Definition

    • In this type of study, two groups are selected- one of people with the disease (case) and the other of people without the disease (control)
    • Compares past exposure in both groups

    Term

    Incidence E+ / Incidence E-

     

              A/A+B

       RR= ________

     

             C/C+D

    Definition
    What is the formula for risk ratio?
    Term
    possible bias
    Definition
    What is a disadvantage of a Case-control Study?
    Term

    • Useful for rare cases
    • inexpensive
    • quick results

    Definition
    What are some advantages of Case-Control Studies?
    Term

    # of deaths of specific disease/# of people who had the disease

     

    x100

    Definition
    What is the formula for Case Fatality Rate?
    Term

    annual death count / total population mid point in time

     

    x100 or x1000

    Definition
    What is the formula for Crude Annual Death Rate?
    Term
    Incubation period
    Definition
    Time from infection to clinical symptoms
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