The usual practice of modeling only randomized controlled trial data at the time the decision on conditional reimbursement is made can lead to wrong decisions. Additional uncertainties arising from outcomes studies should be anticipated at an early stage and included in the model because this can have a strong impact on the prioritization of further research.

Despite the considerable burden and costs of illness and despite the increasing need to set priorities on the basis of efficiency considerations, only 20 economic appraisals of asthma and COPD care have been published during the past 11 years. This paper provides a detailed summary of the cost-effectiveness 'evidence' given by these studies and a discussion of relevant methodological issues. The studies comparing programme costs of delivery methods for oxygen and for aerosol bronchodilator drugs, provide the most straightforward evidence in favour of the concentrator and the metered dose inhaler respectively. There also seems to be evidence in favour of hospital-based home care programmes as compared to community-based home care programs. Health education, especially directed at asthmatic children seems to reduce health care costs and improve attitude, compliance behaviour and self-management skills. Information on the cost-effectiveness of pharmacotherapy and diagnostic technologies, both important interventions in asthma and COPD, was found to be totally lacking.