4) Crude,Specific and Adjusted Rate

8/12/2019 4) Crude,Specific and Adjusted Rate

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CRUDE, SPECIFIC

andADJUSTED RATE


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CRUDE RATE

Definition:

Summary rates based on theactual numberof events (e.g.

births, deaths) in a total

population over a given time

period


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Example:

CRUDE BIRTH RATE:Number of live births to residents in an

area in a calendar year

Average population in the area in that year

CRUDE DEATH RATE:

Number of deaths among residents in an


Average population in the area in that year


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CRUDE RATE

Ignore different risk of morbidity andmortality among subpopulation

Different age groupdiffer in risk of death

Different sex groupdiffer in risk of disease

Differences between characteristicscompositionwill create differences in

crude rates even where rates specific for

those characteristics are the same


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When we compare two conditions

using Crude rates

The results still confounded by somecharacteristics (age, sex, level of

education, social economy etc)


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SPECIFIC RATE

Definition:

Summary rates based on the

actual numberof events (eg.

morbidity, deaths) in a

subpopulationover a giventime period


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Example:

INFANT MORTALITY RATIO:Number of deaths among 0-11 months children in

an area in a calendar year

Number of live births in an area in a calendar year

CAUSE SPECIFIC DEATH RATE FORTBC:

Number of deaths among people with TBC in an


Number of people in an area in a calendar year


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TBC Not TBC Total

Male 12(4%)

300

( 96%)

312

(100%)

Female 20(4%)

500

(96%)

520

(100%)

Total 32 800 832(100%)

SPECIFIC PROPORTION OF TBC MORBIDITY

BASED ON SEX

37,5% 37,5%

62,5% 62,5%

100% 100%


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TBC NOT TBC Total

0 35 y.o 10(3,8%)

250

(96,2%)

260

(100%)

> 35 y.o 22(3,8%)

550

(96,2%)

572

(100%)

32 800 832

(100%)

SPECIFIC PROPORTION OF TBC MORBIDITY

BASED ON AGE

31,5% 31,3%

68,5% 68,7%

100% 100%


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SPECIFIC PROPORTION OF TBC

MORBIDITY BASED ON AGE AND SEX

TBC Not TBCTotal

Age Male Female Male Female

0 - 35

y.o

5(4,8%)

(32,7%)

7(4,5%)

(35%)

100(95,2%)

(33,3%)

150(95,5%)

(30%)

260

(100%)

> 35 y.o

7

(3,8%)(58,3%)

15

(3,8%)(65%)

200

(96,2%)(66,7%)

350

(96,2%)(60%)

572

(100%)

Total12

(100%)

20

(100%)

300

(100%)

500

(100%)

832

(100%)


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ADJUSTED RATE

DEFINITION:Fictitioussummary rates constructed to

permit fair comparisonbetween groups

differing in some important

characteristics


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Statistical procedures to remove

the effect of differences incompositionfor any comparison

Examples of Characteristicscomposition:

Age, Sex, Education, SocialEconomy, Risk Behavior etc


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Example in comparison using

Crude Rate

Mortality rates (CDR)in Indonesia and US

INDONESIA5,8/1000 population

US

9,0/1000 population

Rate ratio = 5,8/9,0= 0,64

Conclusion: ????

INDONESIAyounger

USOlder


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Proportion of Indonesia Population based on

age specific mortality and crude mortality

Age group Number of

People

Proportion Mortality

specific

per 1000

Number of

Deaths

0 14 2000 0,4 2,0 4

15 44 2500 0,5 6,0 15

45+ 500 0,1 20,0 10

0 45+ 5000 1,0 9,0 29

CDR = 29/5000 x 1000 = 5.8 per 1000 population


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Proportion of US Population based on age,

specific mortality and crude mortality

Age group Number of

People

Proportion Mortality

specific

per 1000

Number of

Deaths

0 14 1500 0,3 2,0 3

15 44 2000 0,4 6,0 12

45+ 1500 0,3 20,0 30

0 45+ 5000 1,0 9,0 45

CDR = 45/5000 x 1000 = 9.0 per 1000 population


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Remove the effects of differences in

composition

Calculate the Adjusted Rate

DIRECT method INDIRECT method

Depend on the avai lable data

Greenberg , p . 48 - 53


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CONTOH:

Umur

Penduduk

standar

Angka kematian

spesifik per 1000

Jumlah kematian

expected

A B A B

0 - 14 3500 2 2 7 714 - 44

4500 6 6 27 27

45 + 2000 20 20 40 40

0 - 45 + 10000 9 5.8 74 74

Adjusted rate penduduk A = 74/10.000 X 1000

Adjusted rate penduduk B = 74/10.000 x 1000


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Sources of error

1. Random error/sampling error

2. Systematic error/bias

measurementbias

primary data, secondary data,

acute diseases, chronic diseases,prevalence, incidence


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THANK YOU

Documents

4) Crude,Specific and Adjusted Rate