FINALS: EPIDEMIOLOGY Flashcards
Study of distribution and determinants of health-related event
EPIDEMIOLOGY
EPIDEMIOLOGY COMPONENTS:
GOAL: GENERATE hypothesis
1. Distribution of health-related space
2. Describes the pattern of disease as to
a. P – Person
b. P – Place
c. T – Time
DESCRIPTIVE OR ANALYTIC?
DESCRIPTIVE
EPIDEMIOLOGY COMPONENTS:
GOAL: TEST hypothesis
1. Determination of health-related states
a. Understanding the causes of risk
factors that lead to the disease
- Designs
a. Cross-sectional
b. Longitudinal
i. Prospective - Observational: Cohort study
- Interventional: Experimental
ii. Retrospective - Case control
DESCRIPTIVE OR ANALYTIC?
ANALYTIC
EPIDEMIOLOGY FUNCTIONS
- DESCRIBE HEALTH STATUS
- EXPLAIN CAUSES
- PREDICT
HISTORY
shoe leather theory
A. HIPPOCRATES
B. ROBERT KOCH
C. JOHN SNOW
D. THOMAS DRAWBER
JOHN SNOW
HISTORY
germ theory
A. HIPPOCRATES
B. ROBERT KOCH
C. JOHN SNOW
D. THOMAS DRAWBER
B. ROBERT KOCH
HISTORY
- pneumonia among American Legion Convention attendees in Philadelphia Hotel (1976)
A. FRAMING HEART STUDY
B. LEGIONNAIRE’S DISEASE
C. BRITISH DOCTORS STUDY
D. TOXIC SHOCK SYNDROME
B. LEGIONNAIRE’S DISEASE
HISTORY
- use of tampons among menstruating women (1980)
A. FRAMING HEART STUDY
B. LEGIONNAIRE’S DISEASE
C. BRITISH DOCTORS STUDY
D. TOXIC SHOCK SYNDROME
D. TOXIC SHOCK SYNDROME
HISTORY
- by Thomas Drawber
- risk factors for development of Coronary Heart Disease (1948)
A. FRAMING HEART STUDY
B. LEGIONNAIRE’S DISEASE
C. BRITISH DOCTORS STUDY
D. TOXIC SHOCK SYNDROME
A. FRAMING HEART STUDY
HISTORY
- R. Doll and R. Peto (1951) – smoking and death among british docs – harmful effects of during smoking
A. FRAMING HEART STUDY
B. LEGIONNAIRE’S DISEASE
C. BRITISH DOCTORS STUDY
D. TOXIC SHOCK SYNDROME
C. BRITISH DOCTORS STUDY
Theories of Disease Causation
– linearity, cause precedes the
effect
A. CONFOUNDERS
B. CAUSATION
C. RISK FACTORS
D. ASSOCIATION
CAUSATION
CAUSATION
- Specific agent, specific disease
(Agent – Disease)
SPECIFIC CAUSATION OR MULTIPLE CAUSATION?
SPECIFIC CAUSATION
CAUSATION:
i. Interplay of different components
1. Susceptible host + Pathogenic Agent + Environment = DISEASE
ii. Sufficient component cause
1. Each component should be present
2. C1+C2+C4+C5=Disease
SPECIFIC CAUSATION OR MULTIPLE CAUSATION?
MULTIPLE CAUSATION
Theories of Disease Causation
a. Personal behavior/ lifestyle/ practices
b. Environmental exposure
c. Genetic makeup (predisposing factor)
A. CONFOUNDERS
B. CAUSATION
C. RISK FACTORS
D. ASSOCIATION
C. RISK FACTORS
(it is not the cause but only the “ENABLE”)
Theories of Disease Causation
a. Identifiable relationship
b. Associated variables mean that they co-exist
c. Does not necessarily imply cause and effect relationship
A. CONFOUNDERS
B. CAUSATION
C. RISK FACTORS
D. ASSOCIATION
D. ASSOCIATION
Theories of Disease Causation
a. Extraneous variables whose effect may influence the relationship of the variables to be studied on
b. It has to be “controlled” since it has an influence to both cause and effect;
“without the confounder, the causation will not push thru”
A. CONFOUNDERS
B. CAUSATION
C. RISK FACTORS
D. ASSOCIATION
A. CONFOUNDERS
Set of standard criteria for deciding whether an individual ha sa disease or
health event of interest
A. PROPORTION
B. RATE
C. CASE
D. PERSON TIME
CASE
CASE:
e.g. Syndromes; Chronic and Psychiatric Diseases
CAUSAL OR MANIFESTATIONAL CASE?
MANIFESTATIONAL CASE
CASE:
e.g. Infections
CAUSAL OR MANIFESTATIONAL CASE?
CAUSAL
Natural History of Disease:
– infectious disease
INITIATION OR INDUCTION?
INITIATION
Natural History of Disease:
– non- infectious disease
INITIATION OR INDUCTION?
INDUCTION
PHASE OF DISEASE: Underlying economic/social/environmental/conditions leading to causation
e.g. helmet use/ wash of hands
GOAL: Minimize hazard
A. PRIMORDIAL
B. PRIMARY
C. SECONDARY
D. TERTIARY
PRIMORDIAL
PHASE OF DISEASE: Specific causal factor
Eg. HPV vaccine
GOAL: Reduce INCIDENCE of disease
A. PRIMORDIAL
B. PRIMARY
C. SECONDARY
D. TERTIARY
PRIMARY
PHASE OF DISEASE: early stage of disease
GOAL: reduce PREVALENCE of disease by shortening duration
A. PRIMORDIAL
B. PRIMARY
C. SECONDARY
D. TERTIARY
PHASE OF DISEASE: Late stage
GOAL: reduce the number and impact of complication
A. PRIMORDIAL
B. PRIMARY
C. SECONDARY
D. TERTIARY
TERTIARY
EPIDEMIOLOGIC APPROACH FLOW
- EXAMINE EXISTING FACTS
- GENERATE NEW HYPOTHESIS
- TEST HYPOTHESIS
- CONCLUDE/GENERATE NEW FACTS
Components of an Epidemiologic hypothesis
- Cause is considered
- Anticipate the effect
- Characterize the population
- Exposure-response is established
- Time-response relationship
Method of hypothesis testing:
o There is a common circumstance in
agreement with all instance
o E.g. common factor X results to
disease Y
A. METHOD OF AGREEMENT (COMMONALITY)
B. METHOD OF DIFFERENCE
C. CONCOMITANT VARIATION
A. METHOD OF AGREEMENT (COMMONALITY)
Method of hypothesis testing:
o Level of severity
o Eg. More factor X results to Severe
form of disease than those with less
factor X
A. METHOD OF AGREEMENT (COMMONALITY)
B. METHOD OF DIFFERENCE
C. CONCOMITANT VARIATION
C. CONCOMITANT VARIATION
Method of hypothesis testing:
o Disease A = has factor X Y Z; Disease
A = W Y Z; therefore Disease A is not caused by Factor X
A. METHOD OF AGREEMENT (COMMONALITY)
B. METHOD OF DIFFERENCE
C. CONCOMITANT VARIATION
B. METHOD OF DIFFERENCE
Descriptive Epidemiology:
- Detailed account of a patient’s
experience and clinical manifestation
that comprise a new or an atypical
health event or disease
Eg. VACTRL syndrome
A. CASE REPORT
B. CASE SERIES
C. PREVALENCE STUDIES
D. ECOLOGICAL STUDY
A. CASE REPORT
Descriptive Epidemiology:
- Multiple case reports in one disease
A. CASE REPORT
B. CASE SERIES
C. PREVALENCE STUDIES
D. ECOLOGICAL STUDY
B. CASE SERIES
Descriptive Epidemiology:
- Determine proportions of individuals
with the disease or a health event in a
defined population at a GIVEN TIME
E.g. parasitism among children
A. CASE REPORT
B. CASE SERIES
C. PREVALENCE STUDIES
D. ECOLOGICAL STUDY
C. PREVALENCE STUDIES (existing case) or INCIDENCE STUDIES (new case)
Descriptive Epidemiology:
- Aka correlational study
- Correlation of factors in different
groups
A. CASE REPORT
B. CASE SERIES
C. PREVALENCE STUDIES
D. ECOLOGICAL STUDY
D. ECOLOGICAL STUDY
Analytical Epidemiology:
- Counterfactual Scenario/ Alternative History
- The “what if” in epidemiology
- An alternative parallel timeline that differ from reality
- Contingency tables
- Measurement of exposure and outcome variables at one time point
ANALYTICAL STUDIES
Measured at one point of time
CROSS - SECTIONAL or LONGITUDINAL?
CROSS - SECTIONAL
CANNOT be measured at one point of time
CROSS - SECTIONAL or LONGITUDINAL?
LONGITUDINAL
- Aka Prevalence study
E.g. survey of group with exposure and
without
A. CROSS-SECTIONAL
B. COHORT STUDY
C. RETROSPECTIVE COHORT STUDY
D. CASE CONTROL STUDY
E. EXPERIMENTAL STUDY
A. CROSS-SECTIONAL
- Prospective study between with exposure and without exposure
A. CROSS-SECTIONAL
B. COHORT STUDY
C. RETROSPECTIVE COHORT STUDY
D. CASE CONTROL STUDY
E. EXPERIMENTAL STUDY
B. COHORT STUDY
- Aka historical cohort study
- Retrospective study between group with or without exposure and its present outcome (with or without the disease)
A. CROSS-SECTIONAL
B. COHORT STUDY
C. RETROSPECTIVE COHORT STUDY
D. CASE CONTROL STUDY
E. EXPERIMENTAL STUDY
C. RETROSPECTIVE COHORT STUDY
- Aka trohoc study
- Outcome is MEASURED AT PRESENT TIME and E of the participants in the past is estimated
- Subjects should be the SAME
1. Eg. All should be 7 yrs old, same
outcome
A. CROSS-SECTIONAL
B. COHORT STUDY
C. RETROSPECTIVE COHORT STUDY
D. CASE CONTROL STUDY
E. EXPERIMENTAL STUDY
D. CASE CONTROL STUDY
- A cohort study with MANIPULATION OF EXPOSURE or non exposure with
randomization - Cohorts are randomly assigned
A. CROSS-SECTIONAL
B. COHORT STUDY
C. RETROSPECTIVE COHORT STUDY
D. CASE CONTROL STUDY
E. EXPERIMENTAL STUDY
E. EXPERIMENTAL STUDY
Measurements in Epidemiology:
- To investigate distributions and determinants of disease, it is necessary to know the following:
● Size of the population
● Time period during which data were collected
A. QUANTIFICATION OF DISEASE OCCURRENCE
B. MEASURES OF DISEASE FREQUENCY
C. MEASURE OF OCCURENCE
QUANTIFICATION OF DISEASE OCCURRENCE
● a/b
● Obtained by dividing one quantity by another without implying relationship between the numerator and
the denominator
RATIO
RATIO:
- Type of ratio in which who are
included in the numerator are also
included in the denominator
- a/a+b
A. PROPORTION
B. PERCENTAGE
C. RATE
A. PROPORTION
RATIO:
-There is a distinct relationship between the numerator and denominator
b. Time – included in the denominator
A. PROPORTION
B. PERCENTAGE
C. RATE
C. RATE
Quantify how often disease occurs in a population that is given
A. QUANTIFICATION OF DISEASE OCCURRENCE
B. MEASURES OF DISEASE FREQUENCY
C. MEASURE OF OCCURENCE
B. MEASURES OF DISEASE FREQUENCY
MEASURE OF OCCURENCE:
- NEW RATE
● Incidence proportion (risk)
● Incidence rate (incidence density)
INCIDENCE OR PREVALENCE?
INCIDENCE
MEASURE OF OCCURENCE:
- PRESENT CASES
● Number of total cases
INCIDENCE OR PREVALENCE?
PREVALENCE
TYPES OF POPULATION:
- Aka COHORTS
- NO GAINS for members after it is
established but may be reduced due to
losses (e.g. death)
- if members are no longer at risk hence
called now a CASE
CLOSED OR OPEN POPULATION?
CLOSED POPULATION
TYPES OF POPULATION:
- Aka DYNAMIC
- ADDS NEW MEMBERS through birth and immigration and lose through death and emigration
- Through time, the open population MAY GROW, REMAIN CONSTANT or DECLINE
CLOSED OR OPEN POPULATION?
OPEN POPULATION
NUMBER OF NEW CASES that develop in a population at risk during a specified time interval
- The disease is assessed in a population that is initially disease free but at risk to develop the disease
A. MEASURES OF DISEASE FREQUENCY
B. MEASURE OF INCIDENCE
C. MEASURE OF OCCURENCE
B. MEASURE OF INCIDENCE
Basic Formulation of Incidence Measures:
- MEASURE OF EVENTS – transition from diseased state, thus can be a measure of risk
NUMERATOR OR DENOMINATOR?
NUMERATOR
Basic Formulation of Incidence Measures:
- individuals who are at risk and who
was at risk and now acquired the
disease state
NUMERATOR OR DENOMINATOR?
DENOMINATOR
Basic Formulation of Incidence Measures:
- Proportion of individuals who become diseased during the SPECIFIED PERIOD OF TIME
- (no.of new cases given a period of time)/(total population at risk)
- Assumes the entire population is at risk at the beginning of the study period that was followed over a
specified time interval for the development of outcome under investigation
INCIDENCE PROPORTION OR INCIDENCE RATE?
INCIDENCE PROPORTION
Basic Formulation of Incidence Measures:
- Called force of morbidity or mortality or incidence density
- Measures INSTANTANEOUS RATE of development of disease in a population
- (no.of new case during a period of time)/(total person time of observation)
- Represent the speed or intensity at which the populations are expected to generate new cases
- Reflects the incidence proportion (risk) of the disease when the disease is rare
INCIDENCE PROPORTION OR INCIDENCE RATE?
INCIDENCE RATE
- AMOUNT OF TIME THE PERSON IS OBSERVED during the study, and is counted only when a person is at risk
of being detected as a case - Not counted after:
1. The person DEVELOPS THE DISEASE under investigation
2. The person WITHDRAWS from the study
3. The STUDY ENDS - Add the time of every case until the person developed the disease
PERSON TIME
- Sum of individual’s time at risk or time
each person remained under observation and free from disease
Individual Person time is _________
KNOWN OR NOT-KNOWN?
KNOWN
- Total person time = average population
size x length of follow-up periods - Average population = population at start + population at the end/2
Individual Person time is _________
KNOWN OR NOT-KNOWN?
NOT-KNOWN
- Quantifies the proportion of individuals in a population who HAVE THE DISEASE a specified time
- Snapshot through the population at a point in time to determine who has the disease and who does not
= (no.of existing cases)/(total
population) x 100
A. PREVALENCE
B. INCIDENCE
C. POINT IN TIME
PREVALENCE
- SPECIFIC POINT IN CALENDAR
eg. Onset of menopause, Menarche - Fixed point in the course of events that varies in real person to person
A. PREVALENCE
B. INCIDENCE
C. POINT IN TIME
C. POINT IN TIME
Relationship between prevalence ad incidence
P = I x D
Relationship between prevalence ad incidence
ASSUMPTIONS
Incidence of the disease is ________
over time
CONSTANT OR NOT CONSTANT?
CONSTANT
Relationship between prevalence ad incidence
ASSUMPTIONS
Duration of the disease is ________
over time
CONSTANT OR NOT CONSTANT?
CONSTANT
Relationship between prevalence ad incidence
ASSUMPTIONS
Prevalence of the disease is ______
low <10% or high <10% ?
low <10%
- An important and useful measure of the burden of disease in a community
● Prevalence data may be suggested if not confirmatory of the etiology of certain diseases
Prevalence Measures
- UPSURGE OF CASES in a defined geographic region or easily defined sub-population
- MORE CASES than expected given area, group of people and period of time
- Usually comes to the attention of PH units by:
1. Epidemiology surveillance system
2. Direct notification
A. EPIDEMIC
B. OUTBREAK
C. PANDEMIC
D. DISEASE CLUSTER
OUTBREAK
- outbreak on a larger area
- Occurrence of more cases of a disease than expected over a larger area than that experienced in an outbreak
A. EPIDEMIC
B. OUTBREAK
C. PANDEMIC
D. DISEASE CLUSTER
EPIDEMIC
- aggregates of cases in an given area,
group of people and period of time regardless if the number of cases is more than expected - The used population size at risk is UNKNOWN
A. EPIDEMIC
B. OUTBREAK
C. PANDEMIC
D. DISEASE CLUSTER
D. DISEASE CLUSTER
Factors affecting to mount outbreak investigation
a. Number of cases is significantly higher than expected
b. Scale and severity
c. Potential for spread
d. Political and public health consideration
e. Resource availability
Agencies Involved in an Outbreak Investigation
a. Local health departments
b. Higher level health agencies (DOH-Epid Bureau)
Objectives of Outbreak Investigation
a. ASSESS THE EXTENT of the outbreak
b. REDUCE THE NUMBER OF CASES associated with the outbreak by identifying and eliminating the source
c. IDENTIFY NEW DISEASES syndromes
d. ASSESS EFFICACY of employed prevention strategies
e. ADDRESS LIABILITY CONCERNS, measures damage
f. TRAIN EPIDEMIOLOGIST
g. PROVIDE GOOD PUBLIC RELATIONS and public education
Steps in an Outbreak Investigation (US CDC 1992)
- PREPARE FOR FIELDWORK
- ESTABLISH OUTBREAK
- VERIFY DIAGNOSIS OF CASES
- ESTABLISH CASE DEFINITION AND SEARCH FOR ADDITIONAL CASES
- CONDUCT DESCRIPTIVE EPIDEMIOLOGICAL STUDIES
Prepare field work:
1. Travel arrangements
2. Supplies, equipment, logistics
3. Administrative and scientific contacts
A. ADMINISTRATIVE
B. PERSONAL
ADMINISTRATIVE
Prepare field work:
1. Knowledge updates
2. Understanding of role in the field
3. Familiarity of the chain of authority involved in the process
A. ADMINISTRATIVE
B. PERSONAL
PERSONAL
i. POINT SOURCE EPIDEMIC
ii. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
iii. SPORADIC
iv. PROPAGATED EPIDEMIC
EPIDEMIC CURVE OR EPIDEMIC MAPS?
EPIDEMIC CURVE
i. Dot maps
1. Geographical extent
2. Evidence of clustering
EPIDEMIC CURVE OR EPIDEMIC MAPS?
EPIDEMIC MAPS
EPIDEMIC CURVE
-EXPOSED to the SAME TIME in a short period of time
- PEAK
A. POINT SOURCE EPIDEMIC
B. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
C. SPORADIC CURVE
D. PROPAGATED EPIDEMIC
A. POINT SOURCE EPIDEMIC
EPIDEMIC CURVE
- plateau
A. POINT SOURCE EPIDEMIC
B. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
C. SPORADIC CURVE
D. PROPAGATED EPIDEMIC
B. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
EPIDEMIC CURVE
- common intermittent
source
- CURVE IS JAGGED
A. POINT SOURCE EPIDEMIC
B. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
C. SPORADIC CURVE
D. PROPAGATED EPIDEMIC
C. SPORADIC CURVE
EPIDEMIC CURVE
- Disease spread is person to person with INCREASING NUMBER OF CASES in each generation
- Progressively TALLER PEAKS
A. POINT SOURCE EPIDEMIC
B. CONTINUOUS COMMONS SOURCE OR EPIDEMIC
C. SPORADIC CURVE
D. PROPAGATED EPIDEMIC
D. PROPAGATED EPIDEMIC
