Longitudinal studies to search for predictors of patient outcome

To ensure quality and cost-effectiveness of innovations in health care, a thorough evaluation of care protocols and investments is necessary. In this paper it is pointed out that such an evaluation should not only include the short-term assessment of patient outcome, but also has to comprise longer term effects. This creates the need for longitudinal studies during which the patient is followed during the entire or at least a significant part of the care process. Such an approach brings about several methodological, scientific and technological implications that are common to all longitudinal studies. By presenting the experiences with a large European multi-center study, the paper discusses a number of relevant issues related to the management of time, costs and quality in longitudinal studies that aim at assessment of long-term patient outcome.