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GOOD EVENING
PRESENTED BY,Mrs. B.kalpana, m.sC (N)ASSo. PROFESSORDEPT OF COMMUNITY HEALTH NURSINGSREE NARAYANA NURSING COLLEGENELLORE
Why?
Epidemiological studies are based on sick and well people to determine the crucial difference between those who get disease and those who are spared…………….
An epidemiological studies are aimed to find……………. Nature and extent of the disease Causative agent Sources of infection Period of communicability Mode of transmission Susceptibility of population Incubation period Method of prevention and control
“ The epidemiological investigation to health problems involves the two basic approaches”
Epidemiological approach
a. Asking questionsb. Making comparisons
a. Asking QuestionsThe key information can be approached
through a series of questions
Related to health events What are the actual and potential health
problems its manifestations and characteristics?
Who are affected, with reference to age, sex, social class………?
Where are they occur in terms of place? Which populations are increased at
risk? When does it happen in terms of day,
month, season etc……….?
Why does it happen in terms of contributing or causative factors?
Which problems have declined? Which problems are increasing or have
the risk to increase?
Related to health action What can be done to reduce the problem
and its consequences? How can it be prevented in the future? What action should be taken by the
community to prevent and manage the problem?
Action taken by the health services? Action taken by other sectors? Where and for whom these activities
carried out? What resources are required in future? How are the activities to be organized? What difficulties may arise, and how it
has to overcome?
b. Making ComparisonsThis approach is to make comparisons and draw inferences.Comparison may be made
between different population at a given time eg. Rural with urban population
between sub group of population eg. Male with female population between various periods of observation eg. Different seasons
• Case Counts
• Rates
• Ratios
• Proportions
Tools of Measurement
Case Counts The case count refers to the
number of cases of a disease or other health phenomenon being studied
eg Number of cases of Still births
It Can be useful for allocation of health resources
Rate The rate measures the occurrence of some
particular event ( development of disease or the occurrence of death) in a population during a given period of time.
Expressed as:
Example: Death rate:
n
yx 10
1000year same of populationyear -Mid
year onein deaths ofNumber
A rate comprises the following elements- Numerator, denominator, time specification and multiplier.
The time specification is usually a calendar year
The rate is expressed per 1000 or some other round figure like 100,000.
Various categories of rates1. Crude rate: These are actual observation
rates. Eg: Birth rate, Death rateCrude rates are un standardized
rates2. Specific rate: These are the actual observed
rates due to specific causes (tuberculosis) occurring in specific groups (age-sex) during specific time period (annual, monthly, weekly)
3. Standardized rates: These are obtained by direct or indirect method of standardization
Eg: age and sex standardized rates
Ratio The ratio is the most fundamental
measurement in epidemiology using two variables X and Y
Obtained by dividing one quantity by another with out implying any specific relationship between numerator and denominator
Expressed as: yx
oryx
;
The number of children with scabies at a certain time
The number of children with malnutrition at a certain time
Other examples: Sex-ratio, Doctor-population ratio, Child-woman ratio
Proportion
The proportion is a ratio where the numerator is included in the denominator
Usually proportions are expressed as a percentage
Proportion is the part of the whole
Expressed as
100 timesamein children ofnumber Total
timeaat Scabies ofNumber The
Numerator: It refers to the number of times an event has occurred in a population during specified time period.
It is a component of denominatorDenominator: It may be related to the
population or related to the total eventRelated to population: Mid year population Related to total events: Number of accidents
for 1000 vehicles
OUR ROLE• Screening• Notification• Evaluation of Health Services• Management • Prevention and control
ReferencesActivEpi CD-ROM; Kleinbaum
ActivEpi Companion Textbook; Kleinbaum, Sullivan, Barker
Epidemiology in Medicine, Hennekens
THANK U…