MEASUREMENTS OF MEASUREMENTS OF MORBIDITY AND MORTALITY MORBIDITY AND MORTALITY IN A POPULATION & SOURCE IN A POPULATION & SOURCE

OF ERROROF ERROR

AA. SAGUNG. SAWITRI

KOMANG AYU KARTIKA SARI

Demonstrate ability to search, collect, organize and

interpret information/data from different sources in

order to assist in diagnostic, therapeutic and health

OBJECTIVESOBJECTIVES• Differentiate proportion, ratio, rate, prevalence and incidence.

• Explain four types of incidence based on their denominators.

• Describe the source of numerators and denominators for prevalence and incidence.

• Explain types of errors in rate calculation.

GOALGOAL

CONTENT

• Introduction

• Types of measurement

• More on Incidence and Prevalence

• Specific measurements

• Summary

Introduction

Doctor and Patient

http://www.google.co.id/imgres?imgurl=http://carolynandersonmd.com/wp-content/uploads/2010/05/doctor-connecting-patient.jpg

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Diagnose Treat/therapyDetermine the prognosis

Doctor and Community

Behavior

Health Facilities

Environment

Genetic

Total Population

Illness

Seeking treatment

Hospitalized

Death

Development from healthy in to illness based on severity of illness in the population setting

Natural History and Source of Data

Outcome:

Cure

Control

Disability

Death

Healthy

TreatmentDiagnosisSeek careDiseaseOnset

Symptoms

Data Sources

Survey & Interview in community setting

Doctor/Clinic Record

Hospital Record

TYPES OF MEASUREMENT

JENIS UKURAN

• ANGKA ABSOLUT

• ANGKA RELATIF

– RATIO

– PROPORSI

– RATE INSIDEN, PREVALEN

Absolute Number

FSWs are classified mostly as direct (those who work in brothels and street‐based sex workers) or indirect (such as women working in karaoke bars or massage parlors). It is estimated that there are 95,000-157,000 direct sex workers and 85,000-107,000 indirect sex workers as of 2009. In 2006, the figure was put at 221,000 women working in the sex industry, serving an estimated 4 million clients per year [Sex Work and HIV in Indonesia, 2011].

NUMERATOR

DISTRIBUTION OF PERSONS BITEN BY DOGS PER SUB-VILLAGES AT UNGASAN

No Name of Sub-villages Total Description

1. Giri Darma 15 Death = 2 persons

2. Santi Karya 2

3. Bakung Sari 4 Death = 1 person

4. Sari Karya 7

5. Wijaya Kesuma 2 Death = 1 person

6. Wana Giri 1

7. Dusun Kauh 1

8. Dusun Kelod 8

9. Dusun Kangin 10

10 Santi Karya 3

11. Jaba Pura 0

12 Kaja Jati 0

13 Petangan 0

Jumlah 53 Total deaths 4 persons

Relative Number

n =

NUMERATOR

DENOMINATOR

Ratio• Numerator and Denominator are

independent

• Example– Dependency Ratio– Sex Ratio n =

Proportion• Numerator is part of denominator

n =

Cumulative HIV Cases Per DistrictIn Bali, 1987 - 2011

Bali Provincial Health Dept, Sept 2011

301

732

2179

52

81

138

1059

213

78

Cumulative HIV Cases Per DistrictIn Bali, 1987 - 2011

Bali Provincial Health Dept, Sept 2011

301

732

2179

52

81

138

1059

213

78 15%

1%

22%

45%

4%2%3%

2%6%

Badung

Bangli

Buleleng

Denpasar

Gianyar

Jembrana

Karangasem

Klungkung

Tabanan

RATE

• A proportion when the denominator is a population at risk

n =

population at risk!

MORE ON INCIDENCE AND PREVALENCE

• Proportion of population that not having illness previously and then become ill during the certain period among observed at risk population

• NEW CASES

• RISK OF BEING ILL

INCIDENCE

Numerator / Denominator, Constant, Period 1 2 5 4 3

1. Similar characteristics of N & D

2. Denominator is a “population at risk”

3. During a period of time [time frame]

4. Constant of round number of 10 fold

5. Denominator is a population of certain geographic area

CONDITION

Cumulative Rabies Cases Per DistrictIn Bali, 2008 - 2011

Bali Provincial Health Dept, 2011

18

8

36

26 0

11

21

7

6

# of new cases 2012 = 51 in Denpasar2 in Karangasem2 in Badung

Incidence rate Bali (2012)

= (N/pop at risk)*Constant

= ……..?

Total Population: 3,891,428 persons

1

2

2

RABIES IN BALI, 2008-12 Kabupaten Frek Total Population Proportion Incidence Rate

Jembrana 0 272.828 0

Buleleng 26 662.920 19.5

Tabanan 18 431.172 13.5

Badung 21 (+ 2) 393.020 15.8

Denpasar 11 (+ 1) 523.299 8.3

Gianyar 7 399.660 5.3

Klungkung 8 185.272 6.0

Bangli 6 215.729 4.5

Karangasem 36 (+ 2) 438.475 27.1

Total 133 3.522.375 100.0

Bali Provincial Health Dept, 2011

Natural History of Diseases and Source of Data

Outcome:

Cure

Control

Disability

Death

Healthy

TreatmentDiagnosisSeek careDiseaseOnset

Symptoms

Source of Data

Survey and Interview

Record of doctor/clinic

Hospital Medical Record

Calculating Incidence

• Direct method Primary Data– Interview – Measurement/Assessment

• From Secondary Data– Numerator records (GP/Clinics/hospital/public

health center– Statistic office, estimation from census, census

• Estimating from prevalence

Important Notes!!• Incidence of persons or events?

• Denominator of Incidence?

– “population at risk?” (death, drop out, immune, lost to follow up)

– Availability of data, particularly for the denominator (mid-year, average, beginning plus end divide by 2, etc)

– Person years (person time) Incidence density, cumulative incidence

• Proportion of population who suffer for illness at the time of measurement among the observed at risk population.

• NEW and OLD CASES

• NOT DESCRIBE AT RISK

PREVALENCE

Type of prevalence

• Point prevalence– New and old cases at the point of time

measurement

• Period prevalen– New and old cases at the beginning of

measurement added by new cases on the whole period of measurement

BAGAN

New Cases

Point prevalen

Period prevalen

Cumulative Rabies Cases Per DistrictBali, 2008 - 2011

Bali Provincial Health Dept, 2011

18

8

36

26 0

11

21

7

6

# of new cases 2012 = 51 in Denpasar2 in Karangasem2 in Badung

Total Population: 3,891,428 persons

1

2

2Prevalence at 2008-2011?

RABIES IN BALI, 2008-11 Kabupaten Frek Total Population Proportion Prevalence Rate

Jembrana 0 272.828 0

Buleleng 26 662.920 19.5

Tabanan 18 431.172 13.5

Badung 21 393.020 15.8

Denpasar 11 523.299 8.3

Gianyar 7 399.660 5.3

Klungkung 8 185.272 6.0

Bangli 6 215.729 4.5

Karangasem 36 438.475 27.1

Total 133 3.522.375 100.0

Bali Provincial Health Dept, 2011

Relationship between prevalence and incidence

WHEN (the steady state is in effect):

a) Incidence rate (I) has been constant over time

b) The duration of disease (D) has been constant over time:

ID = P / (1 – P)

P = ID / (1 + ID)c) If the prevalence of disease is low (i.e. < 0.10):

P = ID.

Discuss in your group!Discuss in your group!

How is the relationship between

incidence and prevalence?

SPECIFIC MEASUREMENT

Case Fatality Rate # of Deaths from a Disease # of Cases from that Disease

Survival Rate # of survivors from a Disease # of Cases from that Disease

Attack Rate # of Cases of a Disease Total Population at Risk for a Limited Period of Time

Infant Mortality Ratio?

Maternal Mortality Ratio?

Maternal Mortality Rate?

Crude Death Rate?

Crude Birth Rate?

Incidence Prevalence

Risk to suffer for disease (period of time)

Proportion of suffering disease (point of time)

For acute/chronic For chronic

Application:- Etiology- Management

Application:- Management

COMPARISON BETWEEN INCIDENCE AND PREVALENCE

SUMMARY• 4 Types of Measurements

• Each measurement have:

• Characteristic

• Meaning/Interpretation

• Purpose

• Weakness/advantages

• Understanding measurements will help doctor either as clinician or PH workers to do their job properly