[What lies under the glass on the medical professional's table?]

Normal values are intervals covering the majority of cases detected in healthy individuals. They are gradually replaced by diagnostic criteria based on probability of differentiation between the healthy and ill (prognostic intervals). In 1970-ies, "recommended for health promotion" intervals appeared. The physician must know the origin of the criteria recommended for assessment of the results of the laboratory test or another measurement, in diagnosis, only diagnostic criteria must be used but not criteria designed for prophylactic programs. In the context of each disease diagnostic criteria should account for possible sequelae. Such criteria are multiple: for one test (e.g. plasma glucose concentration) there are different criteria for diagnosis of different diseases (diabetes type 1 or 2, hypothyroidism). Only such criteria should be included in recommendations (standards) on diagnosis and treatment of certain diseases. Conventional "normal values" should be used only in assessment of the results of prophylactic surveys and in search for explanation for the obscure states.