Abstract: A diagnostic method and predictor of prognosis from various therapeutic treatments is provided using discriminant analysis statistics. In one form, a patient is identified as having a disease using discriminant analysis when one or more values of a physiological parameter of the patient is closer to that of a previously characterized group of individuals having a disease and the patient is diagnosed as not having the disease, or healthy, if the value of a patient's parameter is closer to that of individuals previously characterized as healthy, or not having the disease. For example, the parameters can be based on the autonomic and/or enteric nervous system. Advantageously, the present method can be readily adapted using conventional linear discriminant analysis statistics to factor more than one parameter between a patient and one or more previously classified groups, to thereby enhance predictability and reliability of the present method.