Test 1 Flashcards
Incidence is synonymous with? (3)
What is the equation?
new cases of disease/# persons at risk for the disease
Risk, Attack Rate, Cumulative incidence
What types of surveillance are there?
- Active: public health official go into community to search for new diseases/condition cases.
- Passive: Rely on health care system regulations. Health care professionals are required to report certain diseases/conditions.
What is syndromic surveillance?
System that looks for pre-defined signs/systems of patients, either being reported or evaluated?
What is a case definition?
Set of uniform criteria used to define a disease/condition for public health surveillance.
There is a list of diseases that should be reported to CDC’s national notifiable diseases surveillance system (NNDSS).
What are the three Ws of descriptive epidemiology?
What, when, who
Infectivity
The proportion of persons exposed to a causative agent who become infected by an infectious disease?
What is a propagation outbreak?
Outbreak that is spread form person to person.
Usually lasts longer and can have multiple waves of infection if 2 and 3 degree cases occur. Epi curve has a series of progressively taller peaks each an incubation period apart.
Explain what a common source outbreak graph looks like? Give an example of this type of outbreak.
Outbreak in which people are exposed intermittently or continuously to a common harmful source.
Intermittent exposure results in an epi curve with irregular peaks that reflect timing and extend of the exposure.
Continuous exposure: cases rise gradually?
What is a cluster?
This is an epidemic limited to a localized increase in the occurrence of disease.
This is interchangeable with outbreak.
What is an outbreak?
An epidemic limited to a localized increase in the occurrence of disease.
This is interchangeable with cluster.
What is a pandemic?
This is an epidemic that is occurring over a very wide area involving a large number of people - multi-region or multi-national (Likely global).
Example - swine flu
What is an Endemic?
The constant presence of a disease WITHIN A GIVEN AREA or population in excess of normal levels compared to other areas.
Example HIV or Malaria in parts of Africa
What is an epidemic?
General term. The occurrence of disease clearly in excess of normal expectancy.
What is an incubation period?
It is the period of subclinical or inapparent pathologic changes following exposure ending with the onset of symptoms of infectious disease.
Sentinel/Index Case
The initial reported case in a population of an epidemiological investigation.
What is an attack rate?
A variant of an incident rate applied to a narrowly defined population observed for a limited period of time, such as during an epidemic.
What is a latency period?
A period of subclinical or inapparent pathological changes following exposure, ending with onset of symptoms and chronic disease.
Latency is the time period from when you get a pathogen until the body starts responding to the pathogen.
What is an incubation period?
This is the time period between exposure to the onset of symptoms.
How do you find incidence density? Is this appropriate for a dynamic population?
The number of cases of disease/total person-time of population at risk
Yes - this takes into consideration people entering and exiting the population pool, because you are calculating the incident of disease/in a set person population time.
What is the difference between a fixed population and a dynamic population?
Dynamic populations are always fluctuating. This can be approximated by using the average population, mid year popoulation or the population at the beginning of a set time (often the beginning of the year).
Fixed population is easier to study (ex. groups within a longitudinal study)
What does frequency mean in epidemiology?
It is the number of people affected/impacted. (Count)
How do you calculate a cause-specific mortality rate?
It is the mortality rate from a specific cause for a population. You can do this by taking the number of deaths attributed to a specific cause (disease) divided by size of population at midpoint of time interval.
What is a crude mortality rate?
It is the mortality rate from all causes of death for a population. # of deaths/total population.
What is a risk ratio? What is this also called?
This is also called relative risk. It is the ratio of risk from 2 different groups. The reference always goes in the denominator and tested goes in the numerator.
MI risk
Ramipril 0.14
Placebo 0.178
0.14/0.178 = 0.78
Ratio of occurrence (ex MI) with drug/ratio of occurrence without drug=
less than 1 (reduced risk)
greater than 1 (increased risk)
~1 no effect on outcome.
This is saying that the group taking ramipril have a 78% of the risk of having a MI compared to those taking placebo. The Ramipril group has a 0.78 times the risk of having a MI compared to the placebo group. Ramipril group has 22% reduced risk compared to the placebo group.
Point Source Outbreak
Common source outbreak in which the exposure period is relatively brief and all cases occur within one incubation period.
The epi curve has a sharp upward slope and a gradual downward slope.
What is a secondary attack rate?
This is a measure of the frequency of new cases of a disease among the contacts of known cases. Remember to subtract the # of people who have already had the disease from primary exposure.
What is the equation for division of proportions?
Also known as ratio of proportions. This is useful when comparing two different groups - example comparing males to females positive for surgery.
45/50 (group A with outcome/total group A)
/
17/39 (group B with outcome/total group B)
= 2.06
What is the difference between taking absolute difference compared to relative difference?
Absolute difference is subtracting the difference of the two groups outcome, whereas the relative difference is dividing the two.
ARR
Absolute risk reduction aka Attributable Risk (AR)
- defines the risk difference in outcome among “exposed”that can be “attributed” to actual exposure.
- subtract counts
- IR-IR
Ramipril 14%
Placebo 17.8%
ARR=3.8%
There is a 3.8% difference between the placebo and Ramipril groupis attributed to the ramipril exposure.
How do you calculate RRR? How is this interpreted?
Relative Risk Reduction (RRR)
ARR/Runexposed
How do you calculate the NNT? What is this abbrev? ;)
The number needed to treat - this calculation represents the number of patients needed to treat in order to experience one event outcome.
1/ARR
1/Absolute risk reduction (otherwise known as AR attributable risk).
1/0.038~ 27.
