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…