I. M. OKKES, MA, PHD S. K. OSKAM, MSC, PHD H. LAMBERTS, MD, PHD Amsterdam, the Netherlands Submitted, revised, July 24, 2001. From the Academic Medical Centre/University of Amsterdam, Division of Public Health, Department of Family Practice. Reprint requests should be addressed to I.M. Okkes, MA, PhD, Academic Medical Centre/University of Amsterdam, Division Public Health, Department of Family Practice, Meibergdreef 15, 1105 AZ Amsterdam, the Netherlands. E-mail: i.m.okkes@amc.uva.nl.
The value of prior probabilities increases with the availability of data on incidence of diseases in the same population, allowing an estimation of the positive and negative predictive values. Since 1995, data collection has occurred electronically. Later in 2001, a database twice the size will become available that allows more precise estimations for finer age/sex distributions and symptom combinations. Although from Dutch family practice, these data have a high face validity for clinicians wherever they work.8 Nevertheless, it would seem that FPs in the United States and other countries should give priority to collecting their own reliable probability databases.4,22,23
In the Netherlands, Japan, and Poland, an international comparative study has taken place with an electronic patient record, using ICPC. (See page xxx in this issue for the abstract of this article.) Based on a comparison of these databases with US NAMCS data (1995-1997), tables similar to those presented in this paper for the most frequent symptoms and complaints have been made available on the JFP Web site.24.25
