Transcript Morbidity-data sources and measures

Morbidity-data sources and
measures
Farid Najafi
MD PhD
Kermanshah Health Research Center (KHRC)
Kermanshah University of Medical Sciences
Question
References
What are we measuring?
Criteria for diagnosis is the first step (case fefinition)
Different case definition leads to different values
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?
Incidence
• Incidence measures how quickly people are
developing a disease
• Population at risk:
– Cervical cancer
• Women vs. men
• Women after hysterectomy
Relationship between incidence
and prevalence
• Direct relationship between incidence and
prevalence
P=I*D
– 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
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
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
Raw health data
•
Data can be assessed at two levels
1. Summary data
2. 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
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
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
Validity
Health facility data
• Hospital records: usually based on discharge
diagnosis as recorded and coded on the
patient’s 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
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