2. Epidemiologic Indices Flashcards
Why do we address epidemiologic indices or measures?
They provide information regarding the frequency of diseases and associations between exposures and health outcomes
What is the natural history of disease
The courses of disease from its beginning to its final clinical endpoints
What is the population at rink (PAR)?
Those members of the overall population who are capable of developing the disease or condition being studied
What are the common epidemiologic measures?
Proportion percentage and rate
All ratios and ratios are very important for one health
Ratios in one health
The value obtained by dividing one quantity by another
In epidemiology it usually implies that the numerator is not a subset of the denominator
Proportions in one health
A type of ration which number at or is part of the denominator
Usually expressed as percent
Examples of proportions in one health
Incidence (# new cases)
Prevalence (# cases)
Case fatality (# deaths)
Percentages in one health
A proportion that has been multiplied by 100
Formula = (A/A+B) x 100
Rate in one health
Also a type of ration
The denominator involves a measure of time
Examples of rates in epidemiology
Incidence rate (# new cases/PAR)
Prevalence rate (# cases/PAR)
Care fatality rate (#death/PAR)
Define incidence
Referred to the occurrence of new disease or mortality within a defined period of obersation
Cases that exist at the beginning of the period are not counted
Define incidence rate
A rate formed by dividing the number of new cases that occur during a time period by the number of individuals in the population at risk
Most common risk measure
Incidence rate formula
Incidence rate = number of new cases in a time period / total population at risk x 100
Prevalence definition
The unofficial existing cases of a disease or health condition or deaths in a population at some designated time
What are the variations of prevalence
Point prevalence
Period prevalence
Lifetime prevalence
Prevalence vs incidence
Prevalence is the number of EXISTING cases of disease in the population during a defined period
Incidence is the number of NEW cases of disease that develop in the population during a defined period
What are the factors that cause prevalence to increase
Increase incidence
Longer duration of the case
In migration of cases
Prolonged of life of patients without a cure (ex aids)
What are the factor that cause prevalence to decrease
Decreased incidence
Shorter duration of disease
In migration of healthy people
Improved cure rate of disease
What is attack rate
An incidence rate applied to a marro population over a narrow time period
Expressed as percent
What is the formula for attack rate?
AR = new cases in the time period / population at risk at beginning x 100
What is the morbidity rate?
Numerator is the total number of illnesses in a population over a specified period of time
Denominator is the average population at risk over that same time period
What is the formula for morbidity?
Number of illnesses due to the disease in the time period / average number in population during the time period x 100
What is mortality rate?
Numerator is the total number of deaths in a population over a specified period of time
Denominator is the average population at risk over the same time period
Mortality rate formula?
Number of deaths due to the disease in the time period / average number in population during the time period x 100
What is case fatality rate CFR?
The number of deaths due to disease that occur among persons who are afflicted with that disease
What is the formula for Case fatality rate?
Umber of deaths due to disease / number of cases of disease x 100
What is risk factor?
A characteristic of value in predicting risk
Example
Breed, sex, age, weight, activity, nutrition, genetics
What is absolute risk
The rate of occurace is the same as incidence
Formula for relative risk
Incidence rate among exposed / incidence rate of among not exposed
Formula for attributable risk
Incidence rate exposed - incident rate of unexposed
