morbidity measures2

7/29/2019 Morbidity Measures2

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Measures of Morbidity


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James Maxwell, physicist (18311879)


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We owe all the great advances in knowledge

to those who endeavour to find out how

much there is of anything.

James Maxwell, physicist (18311879)


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William Thomson,

engineer, mathematician, and physicist (18241907)


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If you can measure that of which you speak,

and can express it by a number, you know

something of your subject, but if you cannot

measure it, your knowledge is meager and

unsatisfactory.

William Thomson, engineer, mathematician,

and physicist (18241907)


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Sources of data for illness


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Measures of Morbidity

Incidence

Prevalence


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Incidence

Measured by incidence rate:

the number of new cases of a disease thatoccur during a specified period of time in a

population at risk for developing the disease.


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Incidence rate

Cumulative Incidence

Incidence density


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Cumulative Incidence

(Number of new cases during a given period of

time/Population at risk during the same time

period) x 1000


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Example

Among 60 people attending a 12-month

residential detoxification program in Mysore,

50 tested HIV negative at the start of the

program in January 1998. At the end of the

program in December 1998, 3 of the 50

participants tested positive for HIV.

Calculate the cumulative incidence.


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Incidence Density

Number of new cases during a given period

Total person-time of observation


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Uses of Incidence rates

Measures the risk of acquiring the disease

To identify the cause or etiology of disease

To explore the relationship between anexposure and the risk of disease


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Prevalence

Measured by Prevalence Rate

Divided into two types:

1. Point prevalence rate2. Period prevalence rate


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Proportion of individuals in aspecified population at risk whohavethe disease of interest at a

given point in time.

POINT PREVALENCE RATE


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Proportion of individuals in a

specified population at risk whohavethe disease of interest over aspecified period of time.

Annual prevalence rate

(When the type of prevalence rate is notspecified it is usually point prevalence)

PERIOD PREVALENCE RATE


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Relation between Incidence and

Prevalence


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When Insulin was introduced for the first time,

what happened to the prevalence of diabetes?


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Relation between Incidence and

Prevalence

Prevalence = Incidence Duration of disease

P= I x D


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City Population

screened

Positive CXR for TB

Mysore 1000 100

Mandya 1000 60


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City Population

screened

Positive CXR

for TB

Prevalence Incidence

Mysore 1000 100 100 4

Mandya 1000 60 60 20


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City Prevalence Incidence Duration

Mysore 100 4 25 years

Mandya 60 20 3 years


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Uses of Prevalence rates

Measures -burden of disease in a community.

Eg:

How many people in the community have arthritis?

To determine

-how many clinics are needed

-what types of rehabilitation services are needed

-how many and what types of health professionals areneeded.

Needed for planning health services.

To make future projections and

To anticipate the changes


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Exercises-1

In 2005 all the children in Government schools

of Nanjangud were examined for evidence of

leprosy. The procedure was repeated again in

2006. The following were the results:

2005:

a. No. of children on the rolls- 52,600

b. No. of children examined 48,000

c. No. of children found to have active leprosy - 288


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Exercise 1 contd

2006:

d. No. of children on rolls 54,000

e. No. of children examined for the first time- 6,000

f. No. of active cases among the above 46

g. No. of children re-examined - 40,000

h. No. of old cases among them (i) Active 40

(ii) Inactive 200

i. No. of new cases among the re-examined - 80

morbidity measures2

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