[Fuzzy logic and logistic regression in the decision making for parathyroid scintigraphy study].
OBJECTIVE
To develop and compare two mathematical models, the first one based on logistic regression and the second one on fuzzy sets theory, aiming at defining a laboratory testing-based measure of indication for submitting patients to parathyroid scintigraphy.


METHODS
One-hundred and ninety-four patients with serum calcium and parathyroid hormone available were identified from the data registry of parathyroid scintigraphy of a diagnostic laboratory in São Paulo, Southern Brazil, in the period between January 2000 and December 2004. The logistic regression model was developed using SPSS and the fuzzy model was developed using MatLab software programs. The performances of both models were compared using ROC curves.


RESULTS
The performance of both models were statistically different (p=0.026). The area under the ROC curves were 0.862 (95% CI: 0.811-0.913) for the logistic regression model and 0.887 (95% CI: 0.840-0.933) for the fuzzy model. The latter had the advantage of allowing to making decisions based on parathyroid hormone information within a non-discriminating range of calcium values.


CONCLUSIONS
The mathematical model based on fuzzy sets theory seemed to be more useful than the logistic model in the decision making for scintigraphy indication. However, inferences can be made only regarding model comparison and not for parathyroid scintigraphy itself since the data analyzed was not representative of any population.
Sousa
Clóvis Arlindo de
CA
Departamento de Epidemiologia, Faculdade de Saúde Pública, Universidade de São Paulo, Avenida Dr. Arnaldo 715, São Paulo, SP, Brasil.
Duarte
Paulo Schiavom
PS
Pereira
Júlio Cesar Rodrigues
JC
D002118:Calcium / Q000097:blood; D003661:Decision Support Techniques; D005260:Female; D017143:Fuzzy Logic; D006801:Humans; D016015:Logistic Models; D008297:Male; D010280:Parathyroid Glands / Q000000981:diagnostic imaging*; D010281:Parathyroid Hormone / Q000097:blood; D012372:ROC Curve; D011877:Radionuclide Imaging; D017678:Sex Distribution
D010281:Parathyroid Hormone; D002118:Calcium