Morbidity-data sources and measures

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Morbidity-data sources and measures

• Farid Najafi
• MD PhD
• Kermanshah Health Research Center (KHRC)
• Kermanshah University of Medical Sciences

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Question
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References
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What are we measuring?
Criteria for diagnosis is the first step (case
fefinition) Different case definition leads to
different values
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Prevalence
Prevalence rate is a wrong expression It is a
simple proportion or percentage
Period prevalence it requires a smaller survey
sample to find enough cases For an accurate
estimate. Did your child have diarrhea during
any of the last 7 days?
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Incidence

• Incidence measures how quickly people are
  developing a disease
• Population at risk
• Cervical cancer
• Women vs. men
• Women after hysterectomy

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Relationship between incidence and prevalence

• Direct relationship between incidence and
  prevalence
• PID
• Hepatitis A vs. Hep C
• To measure the prevalence we need to conduct a
  cross-sectional study
• To measure the incidence we need to conduct a
  follow-up study

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Incidence rate versus cumulative incidence

• IR is equivalent to the average speed of a car at
  a particular point in time, e.g. 60 km/hour
• CI is analogous to the distance travelled by a
  car during a specified interval of time, e.g. 60
  Km in one hour

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Measuring disease occurrence using routine data

• Most of our information come from routine data
• Data are not individual base
• No causal association between disease and other
  factors
• We are usually interested in incidence
• Difference between crude, age-specific and
  stadardised incidence and prevalence

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Raw health data

• Data can be assessed at two levels
• Summary data
• Raw counts of health events
• More challenge about morbidity data compared to
  mortality data
• Capturing in a less systematic way
• Scope of information is enormous
• No complete informatin at a local level

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Disease registeries

• It covers only small minority of conditions
• CHD first studied in MONICA Project in the early
  1980s
• Cancer Most countries, most notably in
  Scandinavia, have cancer registries that cover
  the whole country
• Cancer is an ideal candidate for registration
  because of its clear-cut diagnosis, based on a
  single simple record (pathology)
• Many infectious diseases

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Health Surveys

• There are two major challenges
• Representativeness sample has been chosen to be
  representative of whole population
• No inclusion of homeless people
• Those who disagree to participate (response rate)
• Validity the extent to which a survey actually
  measures what it set out to measure

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Validity
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Health facility data

• Hospital records usually based on discharge
  diagnosis as recorded and coded on the patients
  record with varying degreees on misdiagnosis,
  mis-recording and mis-coding
• Not representing the general population
• For fatal and serious conditions, hospital
  records provide useful information
• Lack of unique patients identifier
• No information about condition treated by family
  practioners or n home

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Getting access to the data

• International sources
• World Health Organization (http//www.who.int)
• World Bank (http//www.worldbank.org)
• National data sources
• Ministry of Health

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