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close this bookManual of Epidemiology for District Health Management (WHO; 1989; 202 pages)
View the documentForeword - A.O. Lucas
View the documentPreface and acknowledgements
open this folder and view contentsCHAPTER 1. District Health Management
open this folder and view contentsCHAPTER 2. Epidemiological Principles
open this folder and view contentsCHAPTER 3. District Population
close this folderCHAPTER 4. Epidemiological Health Information
View the document4.1 Health status assessment
View the document4.2 Important diseases
View the document4.3 Sources of epidemiological information
View the document4.4 Morbidity patterns
View the document4.5 Mortality patterns
View the document4.6 Seasonality
View the document4.7 Using morbidity and mortality rates
View the document4.8 Death registration and certification
View the document4.9 District health information checklist
open this folder and view contentsCHAPTER 5. Reporting and Surveillance Systems
open this folder and view contentsCHAPTER 6. Controlling an Epidemic
open this folder and view contentsCHAPTER 7. Epidemiological Surveys
open this folder and view contentsCHAPTER 8. Organizing Investigations and Surveys
open this folder and view contentsCHAPTER 9. Record Forms and Coding
open this folder and view contentsCHAPTER 10. Data Processing and Analysis
open this folder and view contentsCHAPTER 11. Presenting Health Information
open this folder and view contentsCHAPTER 12. Communicating Health Information
open this folder and view contentsCHAPTER 13. Epidemiology and District Health Planning
View the documentCHAPTER 14. A B C of Definitions and Terms
View the documentAPPENDIX 1. Ethical guidelines for epidemiological investigations
View the documentAPPENDIX 2. Estimating sample size for a prevalence studya
View the documentAPPENDIX 3. Using random numbers
View the documentAPPENDIX 4. Organizing an epidemiological survey
View the documentAPPENDIX 5. Screening and diagnostic tests
View the documentAPPENDIX 6. Age standardization
View the documentBack cover

4.3 Sources of epidemiological information

The routine district health information system commonly has information on the frequency and distribution of the locally important causes of morbidity and mortality. However, often this information is not presented in a way that is easy to understand and use.

Morbidity information gives the overall picture of ill health in the community. Although this information is often deficient in quality and quantity in developing countries, the district sources include the following:

• Hospital inpatient records

• Workplace records

• Outpatient records

• Schools

• Disease notifications

• Special surveys

Hospital inpatient records

Analysis of hospital and clinic records can provide high-quality information on the most important causes of major illness in a community, but for them to be useful as an indicator of the health status of the whole population, allowance must be made for the strong tendency for inpatients to come from among people living near the hospital, the wealthier and the better educated. In some countries, many seriously ill patients never reach a hospital if they live far away.

Outpatient clinic records

Records of people attending health centres and health posts as outpatients may provide information, but there are problems in collecting the necessary data. For example, diagnoses are frequently given in terms of the chief complaint or symptoms; attendances are given in terms of total visits rather than by new and repeat visits, and people attending for immunizations or other preventive services may be recorded together with those who have come because they are ill. The information suffers from selection biases similar to those mentioned for hospital records. Although health centres and health posts may cover a wider population than hospitals, patients who live near a facility and who can afford the time and fees, if any, are the people most likely to attend. Such records, however, do provide information about the use made of outpatient facilities and the most frequent complaints, and do help to describe the pattern of disease in a community.

Disease notifications

Notification systems are restricted to a selected list of “important diseases”, which may differ from one country to another. By and large, these diseases are the infectious ones which require prompt action for control. Medical practitioners and other health personnel may have a special responsibility and may be legally required to provide such notifications. The health officer in charge of the district is usually responsible for receiving the notifications and taking the most appropriate action.

Workplaces and schools

Workplaces may provide data on absences due to sickness as well as the results of any periodic health examinations. Data on those employed reflect the situation in a selected sample of people who work; people who are ill may not have been employed in the first place, or they may have had to leave employment because of ill health.

Schools can provide data on absences due to sickness as well as the results of screening programmes by school health services. In countries where school attendance is low the information may be substantially biased and likely to miss those children who are socially and economically disadvantaged.

Special surveys

There are two ways in which important diseases may be under-recognized by district information systems. If the disease has a low frequency (incidence or prevalence) there may be too few cases for them to show up clearly in a poorly functioning health information system - leprosy is a good example. The other way is when the illness does not produce clear symptoms and signs that are easily recognized by the people themselves or the health workers. Schistosomiasis, filariasis and malnutrition are good examples.

Special surveys and research studies are often required in these circumstances, particularly for subclinical and chronic infections such as malaria, African trypanosomiasis, Chagas disease, filariasis, leprosy and schistosomiasis. The same applies to chronic physical and mental disabilities and eye diseases. The importance of poliomyelitis and neonatal tetanus in many developing countries was demonstrated mainly by such special surveys.

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