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Harry de Koning

Prof.dr.H.J. de KoningProfessor of Evaluation of Screening

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Screening is the detection of a disease, condition, abnormality or stunted development at a stage at which no symptoms have appeared yet. The purpose of early detection is to halt or delay adverse progression by offering treatment in an earlier stage than usual. But early detection and prevention at the population level does not guarantee effective prediction at the individual level, and we often need to implement programs for large groups of people, only some of whom will benefit. Stringent standards must therefore be applied when considering which screening programs and tests should be made available. The primary objective of evaluation of early detection programs is to quantify their positive and negative effects on population health.

New insights from fundamental research and technological developments have greatly increased the number of abnormalities that can be detected at an early stage. Modern imaging techniques can show calcification of the most important arteries, osteoporosis or the early stages of dementia. It may even become possible to detect biomarkers in the umbilical cord blood that predict the development of obesity.

In 1968, Wilson and Jungner were the first to try to make sense of the large ocean of possibilities and obscurities of screening. Their 10 old principles nowadays seem to have grown into dogmas, despite the actual spirit of the authors. NEW criteria for early detection (and evaluation) have now been developed, which are universally applicable and unambiguous. There must be substantial positive health outcomes, in terms of additional years of life, improvements in cognitive, motor and/or socio-emotional development, or a significant increase in management or treatment options. These effects must have been established with certainty, if possible by means of a randomised trial. Further, the level of overdiagnosis and adverse side-effects must be limited. The anticipated balance between positive health outcomes and sideeffects must have been clarified prior to possible implementation. There must be a reasonable balance between costs and benefits, and measures must be taken to ensure that implementation will not lead to substantial unintended effects (such as widespread inequality).

Identifying appropriate high-risk groups for participation in screening, adequate screening tests, and optimal time intervals between tests, are all crucial in the evaluation of early detection programs, as is respecting each individual's autonomy and freedom to make choices about participation. This requires coordination and partnerships traversing a range of professions and fields.

I hope that by evaluating screening according to these principles our research team and partners can make a significant contribution to the health of the population.

Harry de Koning