Evaluation of clinical decision aids--more to think about

Validation and clinical testing of medical decision aids is a hot topic at present. We state a few main points which, in our opinion, have not received the attention they deserve. Our main concerns have to do with the statistical design and analysis of field evaluation studies; with long-term effects; and with the interplay between medicine and the software industry. The points represent our reaction to a recent symposium on the topic, published in this special issue. We take the opportunity to supplement the papers at hand in various ways and, where we see a risk of misconceptions or poor practice becoming cemented, try to point out the proper course.