Download - Measurements in epidemiology
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Disease frequency.
Distribution
determinants.
Disease frequency.
Distribution.
Determinants.
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Mortality.
Morbidity.
Disability.
Presence & absence or distribution of..
Medical needs.
Utilization of health services.
Demographic variables.
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Rate
Ratio
Proportion
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Measures the occurrence of an event or disease in a given population during a given period (one Year).
(Birth rate, growth rate, accident rate)
Usually expressed per 100 or per1000 population.
It has a time dimension, whereas a PROPORTION does not.
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A fraction is made up of 2 numbers.
The top number is called the NUMERATOR
and the bottom number is called the DENOMINATOR.
In the fraction ¾ the 3 is the numerator and the 4 is the denominator.
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No of death in one year Death rate= -------------------- X 1000
Total mid year population
Numerator Denominator.Time specificationMultiplier
(Numerator is part of denominator )
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The value obtained by dividing one quantity by another- X/Y.
Male to female ratio.
A ratio often compares two rates,
death rates for women and men at a given age.
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Ratio also expresses relation of size between the two quantities.
Numerator is not part of Denominator.
Expressed as X / Y.
Doctor : Population ratio.
Male : Female ratio.
WBC : RBC ratio
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A part/share or number considered in comparative relation to a whole.
"the proportion of greenhouse gases in the atmosphere is rising”
Usually expressed as a percentage %
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This is also relation /magnitude between two quantities, And numerator is always part of denominator.
And expressed as percentage -Proportion of female students .-Proportion of anemic mothers
(60% mothers are anemic)
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Incidence
Occurrence of new cases
•
Prevalence
Existence of all new & old cases.
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Prevalence:- how many people in a population currently have the disease (Photograph)
Incidence:- how many people are diagnosed each year (Film)
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Cure rate
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New cases
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• The rate at which acute
disease is spreading --
used during epidemics
& expressed in %.
Attack rate
• % of exposed persons
developing disease after
primary case exposure
Secondary
attack rate
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•Prevalence at any
given point of time.
• 4% TB cases on 1st April
Point
prevalence
•Prevalence at a given
period of time.
•Period will be 1year.
Period
prevalence
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Longer duration of the disease.
Prolongation of life, with treatment.
If incidence increases.
Immigration of new cases.
Better reporting of cases.
Emigration of healthy people.
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Longer
duration of
disease
Incidence
increases.
Prolongation
of life
without
cure.
20
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Shorter duration of diseases.
Improved cure rate.
Incidence decreases.
Emigration of new cases.
Under reporting of cases.
Immigration of healthy people.
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Improved cure rate.
Short duration of
disease.
Incidence decreases
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Crude Death Rate.
Specific death rate.
Case fatality rate.
Proportional mortality rate.
Survival rate.
Standardized death rate.
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Number of deaths from all causes, per 1000 estimated mid year population in one year in a given place.
No deaths during one yearCDR = _________________________ X 1000
Mid year population
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Cause Specific death rate like
disease death rate, Road accident…
Age specific-IMR, Child Mortality rate
Sex specific death rate – MMR/female
Period specific death rate–Death in May
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Percentage of particular cases dying during particular disease epidemic.
Killing power of disease particularly acute diseases
No of deaths due to cholera CFR= ----------------------- X 100
Total No of cholera cases
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Proportion or % of deaths due to particular cause out of total deaths.
It measures the disease burden.
Under 5, No of deaths below 5 years
proportional = -------------------- X 100
mortality rate Total No all of deaths
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Percentage of the treated patients remaining alive at the end of 5 years treatment.
Yard stick for assessing the standard of therapy in cancer.
Survival pts alive at the end of 5 yrs
Rate = ---------------------- X 100
Total No of pts treated
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CDR can not be useful for comparison.
Death rate need to be standardized for comparisons.
Standardization can be done by-:adjusting death rate age wise,:also can be done sex/race wise