Objective: The objective of the Diagnostic Compass is to contribute to rational diagnostic testing. The focus is on the application of all diagnostic tests (following anamnese and physical examination) in medical diagnosis. The verb 'contribute' indicates the necessity of cooperation of an instrument like this Compass with other instruments like education, peer review and feedback. 'Rationalizing' diagnostic testing is defined as the optimal foundation of diagnostic procedures on scientific evidence concerning usefulness of a certain test in a specific situation. The Diagnostic Compass, in other words, tries to get the available evidence used in daily practice.

Method: The method is as follows: Diagnostic Compass contains a (1) problem-centered division in which 111 of the most important diagnostic problems are addressed and (2) a test-centered division in which several hundreds of haematological, biochemical, microbiological, X-ray and endoscopic tests are described systematically, including information about safety, effectiveness, indications, interpretation of possible test results and cost.

The guidelines of the Diagnostic Compass are based on scientific evidence or on existing 'Concentrations of evidence' like existing professional guidelines (like the Practice Guidelines of the Dutch CP association). Responsibility for the Quality of the Compass lay with a Committee, in which all relevant professional organisations are represented.

Results: The result is a useful instrument for implementation of results of TA and other sources of 'evidence'. An evaluation of the use and usefulness will take place during the next months. A second edition of the Diagnostic Compass is planned for January 1999.