Diagnosis, diagnostic criteria, and consensus

Clinicians need accurate, reliable diagnostic criteria for the conditions they evaluate because this is the basis for rational, effective treatment and the estimation of a meaningful prognosis. Standardizing diagnostic approaches wherever this is feasible can reduce variations in care. The development of diagnostic scales has the potential to meet this goal. The approaches to the development of these scales should follow the same measurement principles used in the development of outcome instruments. The concept of consensus is fundamental to understanding how we make diagnoses and should be thought of as a potentially flexible and fluid idea that can accommodate the discovery of new knowledge in our efforts to accurately diagnose medical conditions.