One of the common limitations of expert systems for medical diagnosis is th
at they make an implicit assumption that multiple disorders do not co-occur
in a single patient. The need for this simplifying assumption stems from t
he fact that finding minimal sets of disorders that cover all symptoms for
a given patient is generally computationally intractable (NP-hard). In this
paper, we explain the need for performing multi-disorder diagnosis, review
previous approaches, formulate the problem using set theory notation, and
propose the use of a search method based on a genetic algorithm. We test th
e algorithm and compare it to another approach using a simple example. The
genetic algorithm performs well independently of the order of symptoms, and
has the potential to perform multi-disorder diagnosis using existing or ne
wly developed knowledge bases. (C) 2000 Elsevier Science B.V. All rights re
served.