Abstract:
In 1987, the American Rheumatism Association issued a set of criteria for the classification
of rheumatoid arthritis (RA) to provide a uniform definition of RA patients. Fuzzy
set theory and fuzzy logic were used to transform this set of criteria into a diagnostic
tool that offers diagnoses at different levels of confidence: a definite level, which
was consistent with the original criteria definition, as well as several possible
and superdefinite levels. Two fuzzy models and a reference model which provided results
at a definite level only were applied to 292 clinical cases from a hospital for rheumatic
diseases. At the definite level, all models yielded a sensitivity rate of 72.6% and
a specificity rate of 87.0%. Sensitivity and specificity rates at the possible levels
ranged from 73.3% to 85.6% and from 83.6% to 87.0%. At the superdefinite levels, sensitivity
rates ranged from 39.0% to 63.7% and specificity rates from 90.4% to 95.2%. Fuzzy
techniques were helpful to add flexibility to preexisting diagnostic criteria in order
to obtain diagnoses at the desired level of confidence.
Keywords:
Fuzzy Set Theory - Expert Systems - Diagnosis - Rheumatoid Arthritis - CADIAG-2