Computerized clinical guidelines can provide significant benefits in terms
of health outcomes and costs, however, their effective computer implementat
ion presents significant problems. Vagueness and ambiguity inherent in natu
ral language (textual) clinical guidelines makes them problematic for formu
lating automated alerts or advice. Fuzzy logic allows us to formalize the t
reatment of vagueness in a decision support architecture. In care plan on-l
ine (CPOL), an intranet-based chronic disease care planning system for gene
ral practitioners (GPS) in use in South Australia, we formally treat fuzzin
ess in interpretation of quantitative data, formulation of recommendations
and unequal importance of clinical indicators. We use expert judgment on ca
ses, as well as direct estimates by experts, to optimize aggregation operat
ors and treat heterogeneous combinations of conjunction and disjunction tha
t are present in the natural language decision rules formulated by speciali
st teams. (C) 2001 Elsevier Science B.V All rights reserved.