basic measurements in epidemiology
DESCRIPTION
ÂTRANSCRIPT
![Page 1: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/1.jpg)
Basic Measurements In Epidemiology
By Salwa M Osman
![Page 2: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/2.jpg)
The first requirement of measurement is definition of what is to be measured and establishment of criteria or standard by which it can be measured .
![Page 3: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/3.jpg)
The definition Should be: Acceptable.
Applicable to its use in large population.
Valid
![Page 4: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/4.jpg)
Clear definitions help to minimize errors in classification of data.
![Page 5: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/5.jpg)
The scope of measurements in epidemiology is very broad and unlimited and include the following:
Measurements of mortality. Measurements of morbidity. Measurements of disability.
![Page 6: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/6.jpg)
Measurements of the presence ,absence or distribution of the characteristics or attributes of the disease.
Measurements of natality. Measurements of medical needs ,health care
facilities , utilization of health services and other health related _events
![Page 7: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/7.jpg)
.Measurements of the presence ,absence or distribution of the environment and other factors suspecting of causing the diseases.
Measurements demographic variables.
![Page 8: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/8.jpg)
The basic requirements of measurements are: Validity. Reliability. Accuracy. Sensitivity. Specificity.
![Page 9: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/9.jpg)
Tools Of Measurements:
RATE.
RATIO.
PROPORTION.
![Page 10: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/10.jpg)
RATE:
The rate measures the occurrence of some particular events in a population during a given time period .
The rate is a statement of the risk of developing a condition .
The rate indicates the change in some events that takes place in a population over a period of time .
![Page 11: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/11.jpg)
Death rate:
Number of deaths in one year x 1000Mid-year population
![Page 12: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/12.jpg)
It comprises these elements : Numerator Denominator(the numerator is a component of the
denominator) Time specification (usually a calendar year.) Multiplier
![Page 13: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/13.jpg)
The rate is expressed per 1000 or some other round figure (10.000,100.000) selected according to convention to avoid fractions.
![Page 14: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/14.jpg)
Rate categories:
Crude rates.
Specific rates.
Standardized rates.
![Page 15: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/15.jpg)
RATIO:
Ratio is expresses a relation in size between two random quantities .
The numerator is not component of the denominator
The ratio is a result of dividing one quantity by another.
![Page 16: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/16.jpg)
It expressed in form of :
X:Y OR X/Y
For example: The ratio of WBCs relative to the RBCs is 1:600 or 1/600
![Page 17: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/17.jpg)
The proportion is a ratio which indicate the relation in magnitude of a part of the whole
The numerator is always included in the denominator
The proportion is usually expressed as percentage.
PROPORTION:
![Page 18: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/18.jpg)
For example: the number f children with scabies at a certain time x100
the total number of children in the village at the same time
![Page 19: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/19.jpg)
Concept of numerator:
It refers to the number of times an event has occurred in population ,(e.g. sickness ,death ,episodes of sickness ) during a specific time- period .
![Page 20: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/20.jpg)
Concept of denominator :
The numerator has little meaning unless it is related to the denominator .
The denominator may be: Related to the population. Related to the event.
![Page 21: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/21.jpg)
Related to the population: Mid –year population.Because the population size changes daily due
to birth , death and migration.It refers to the population estimated as on first
of July an year .
![Page 22: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/22.jpg)
Population at risk:The term is applied to those to whom an event
could have happened whether it did or not .Sometimes it may be necessary to exclude
people because they are not at risk.
![Page 23: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/23.jpg)
PRSON-TIME:As in cohort study persons may enter the study
at different times in such cases denominator is a combination of persons and time .
The most frequently used is person-years.For example if 10 persons remain in the study
for 10 years it will be 100persons year.
![Page 24: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/24.jpg)
PERSON-DISTANCES: Passenger-mile SUBGROUB OF THE POPULATION: e.g. age ,sex ,occupation , social class ,etc…
![Page 25: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/25.jpg)
Related to total event: In some instance the denominator may be
related to the total event as in accident the number of accident per 1000 vehicle will more useful than total population many of them may be not using vehicle.
![Page 26: Basic Measurements In Epidemiology](https://reader034.vdocuments.site/reader034/viewer/2022052403/568c37f11a28ab02359d5185/html5/thumbnails/26.jpg)
THANK YOU