The use of epidemiological tools in conflict-affected populations: open-access educational resources for policy-makers

Table of Contents

1. Welcome
2. Introduction: Epidemiology in crises
3. Ethical issues in data collection
4. Need for epidemiologic competence
5. Surveys - Introduction
   1. What is a survey?
   2. Types of outcomes and indicators measured in a survey
   3. Reasons to do a survey
   4. Questions to ask before beginning or commissioning a survey
   5. Alternatives to conducting new surveys
   6. Limitations of surveys
   7. Valid questions to answer
   8. Formulation of goals and objectives
6. Surveys - Description of sampling methods
7. Surveys - Sampling error, bias, accuracy, precision, & sample size
8. Surveys - Resources required for surveys
9. Surveys - Critiquing survey reports
10. Surveillance - When to do surveillance
11. Surveillance - Methods
12. Surveillance - Common problems
13. Programme data
14. Rapid assessment
15. Mortality - Indicators and their measurement
16. Mortality - Data sources
17. Mortality - Interpretation and action
18. Nutrition - Introduction and background
19. Nutrition - Indicators and their measurement
20. Nutrition - Data sources
21. Nutrition - Interpretation and action
22. Health services
23. Vaccination programmes
24. Water supply, sanitation, and shelter
25. Violence
26. Presentation of results
27. Formulating conclusions and recommendations
28. Dissemination and action

Limitations of surveys

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When deciding whether or not to carry out or commission a survey, you must keep in mind the limitations of surveys:

Individual surveys are not good at following trends in real time or over short periods of time.

Because surveys collect data at a single point in time, it is difficult to measure changes in the population unless two or more surveys are done at different points in time. Such repetition is often expensive and time-consuming, making frequent periodic surveys impractical.

Individual surveys generally cannot provide strong evidence of cause and effect.

Because surveys collect data on disease and risk factors at the same time, you often cannot tell which came first, the risk factor or the disease. Without this temporal association, it is very difficult to prove that the reputed risk factor actually causes the disease. For example, a survey in a refugee population may find high incidence rates of diarrhoea, a low prevalence of access to clean water, and a high prevalence of malnutrition. However, a single cross-sectional survey cannot disentangle the different contributions of each of these factors to the others; in fact, it is likely that malnutrition and limited access to clean water contribute to high diarrhoea incidence, while the high diarrhoea incidence also contributes to malnutrition.

Other constraints to using surveys to gather data:

• Insecurity limiting access to the population of concern
• The lack of time to carry out a survey
• The lack of funding necessary to carry out a survey
• The lower priority for carrying out a survey because of competing urgent tasks