Historically, in the process of diagnostic decision making, emphasis was on the skills of effective history taking and physical examination. When deemed necessary, simple laboratory tests (eg, blood count, urinalysis) were also performed by the examiner. This flow of information was a powerful way of making the diagnosis. Admittedly, the ambiguous information content of these data frequently had to be interpreted by nonscientific methods; on the other hand, even these vague data when enriched by the good diagnostician's experience and intuition could lead to remarkably accurate diagnoses. For thousands of years this simple system of information flow was the "art of medicine," justifiably the pride of distinguished line of great clinicians, and it should be remembered with considerable nostalgia.
Recent progress in various fields of medical sciences caused a palpable shift in emphasis. Following World War II, the scope of laboratory medicine enlarged at a spectacular rate. The practitioner could