Development and validation of HEPAR, an expert system for the diagnosis of disorders of the liver and biliary tract

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Abstract
HEPAR is an expert system in the field of hepatology which can be used as a supportive tool in the diagnosis of disorders of the liver and biliary tract. The representation language employed in HEPAR consists of production rules with object-attribute-value triples. In the system, medical diagnosis is modelled according to the strategy which is clinically used in this field. The patient's disorder is assessed in two stages. In the first stage, available data from medical interview, physical examination and simple laboratory tests are used to determine whether the disorder is hepatocellular or biliary obstructive in nature, and whether benign or malignant features are present. In the second stage the system produces a subset of possible diagnoses out of a set of more than 80 disease categories, using additional data from supplementary tests. The results of the first stage classification cause considerable pruning of the search space. In this paper the structure, development process and approach followed in the validation of the HEPAR system are described. The results of a recent performance validation study using data from 181 consecutive patient cases are discussed.