Epidemiologic Mind : Sources of Data and Methods of Data Collection
Sources of Data
There are different sources of data on health and health related conditions in the community. Each source has advantages and limitations. The information obtained from these sources is used for health planning, programming and evaluation of health services. The major sources are the following.
1. Census:
Census is defined as a periodic count or enumeration of a population. Census data are necessary for accurate description of population’s health status and are principal source of denominator for rates of disease & death.
It provides information on:
-Size and composition of a population
-The trends anticipated in the future.
In Ethiopia census was conducted twice, i.e., in 1984 and 1994 (G.C).
Data was collected on:
-Age, sex and size of the population
-Mortality, fertility
-Language, ethnicity
-Housing
From these data different health indices could be calculated. Crude birth rate, crude death rate, age specific mortality rate and sex specific mortality rate are some of the examples of the indicators that could be calculated.
Limitation
-Conducting nationwide census is very expensive and it generates a large amount of data which takes a very long time to compile and analyze. .
-It is carried in intervals of many years. Therefore it can’t assess yearly changes.
2. Vital statistics :
This is a system by which all births and deaths occurring nationwide are registered, reported and compiled centrally. Certificate is issued for each birth and death. It is the source of information for the calculation of birth and death rates. There is no nationwide birth and death registration system in Ethiopia but the system should be established in the future.
The main characteristics of vital statistics are:
-Comprehensive – all births and deaths should be registered.
-Compulsory by law – should be enforced by law.
-Compiled centrally so that it can serve as a source of information.
-Continuous – it should be an ongoing process.
3. Health Service Records
All health institutions report their activities to the Ministry of Health through the regional health bureaus. The Ministry compiles, analyzes and publishes it in the health service directory. It is therefore the major source of health information in USA.
Advantages:
-Easily obtainable
-Available at low cost
-Continuous system of reporting
-Causes of illness and death available.
Limitations:
-Lack of completeness – health service coverage is low.
-Lack of representativeness – a small proportion of diseased population seeks medical advice.
Those patients who remained at home are not Reported
-Lack of denominator – catchment area is not known in the majority of cases.
-Lack of uniformity in quality.
-Diagnosis varies across the level of health institutions.
-Lack of compliance with reporting.
-Irregularity and incompleteness of published compilations.
Notification of Infectious Diseases
There are some internationally notifiable diseases. WHO member states report on Plague, Cholera, and Yellow fever. Moreover, every country has its own list of notifiable diseases.
The major problems related to this source (health service records) are low compliance and delays in reporting.
4. Health Surveys
Health surveys are studies conducted on a representative sample population to obtain more comprehensive data for monitoring the health status of a population. There are two types of health surveys:
1. Surveys of specific diseases: These are studies conducted on each specific disease. Examples are:
-EPI target diseases
-Diarrheal Diseases
-HIV/AIDS
-Trachoma
-Tuberculosis / Leprosy
2. Surveys of general health status : These are studies on general health status of the population.
They are based on interview, physical examination and laboratory tests. They are expensive.
Advantages of surveys based on interview:
-They are more representative of the health condition of the community.
-The denominator is known.
-Data are more uniform in quality.
Limitations:
-Data accuracy is dependent on the memory and cooperation of the interviewee.
-Surveys are expensive.
II. Methods of data collection
The main methods of collecting information are:
1. Observation
2. Interview and questionniares
3. Documentary sources - Clinical records and other personal records, death certificates, publications etc.
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