Measurement in epidemiology

Abstract

Data (information) are the building blocks of epidemiological research. Careful measurement, recording and handling of information are crucial to the research process. The nature of the data required must be precisely defined and its collection requires the use of reliable tools or instruments. Standardisation of definitions and procedures used in measurement helps to ensure comparability. Care in undertaking measurements and rigorous training of personnel carrying out the measurements help to ensure precision. Special care is necessary to ensure completeness and accuracy in recording the data. Information may be obtained from routine or especially designed forms and evaluated by counting deaths or cases of disease or measures of dysfunction. Questionnaires are a frequently used instrument for collecting information. They should include data identifying the individual being studied, followed by specific questions concerning diseases and determinants. To be useful, such questionnaires must be carefully structured. Diseases are usually compared by calculating 'rates' or 'risks', consisting of numerators (cases, events) and denominators (population). Prevalence and incidence are standard measures of 'risk'. The collection of high quality information (data) and its use to construct estimates of 'risk' or risk ratios form the basis of epidemiology.