[The Bayesian theorem in clinical differential diagnosis (author's transl)].

New (a posteriori) probablities of medical diagnosis can be calculated by the Bayesian formula from a priori probabilities of the diagnosis or diagnoses under consideration and from the probabilities of a given test result occurring with each disease. Using sequential iteration, the Bayesian formula is applicable to the calculation of a posteriori probabilities after multiple tests have been performed. When this iterative process has been programmed for a pocket calculator it can easily be used in clinical practice. As a consequence, medical knowledge can be applied more rationally. Many inconsistent data can be more easily interpreted as a result. Furthermore, results of diagnostic tests can be used more extensively and normal test results given their full weight.