Reference values for pulmonary function test: suggestions for a correct use and interpretation

This paper describes the complex reasoning activity the respiratory clinician performs while using the respiratory function tests for diagnosing a disease. The probability each functional parameter is belonging to a healthy subject is the first useful measure to start with that reasoning. In a second step, a set of parameters is evaluated to define a functional syndrome and, finally, the identification of the disease underlying that syndrome is the last step of this journey. The comparison of measured parameters with reference data in healthy subjects is crucial to measure the probability at the beginning of the diagnostic reasoning. Reference data are often used also to define the severity of a respiratory disease or to evaluate the efficacy of a therapeutic intervention. Clearly, reference data are used to address quite different tasks, the methodological implications of which are discussed in this paper. In the last part of this paper the authors present their suggestions and some temporary solutions to what is a lack of knowledge for a more sensible utilization of respiratory reference values.