title: Severity classification for idiopathic pulmonary fibrosis by using fuzzy logic.
abstract: OBJECTIVE
  To set out a severity classification for idiopathic pulmonary fibrosis (IPF) based on the interaction of pulmonary function parameters with high resolution computed tomography (CT) findings.
  
  
  BACKGROUND
  Despite the contribution of functional and radiological methods in the study of IPF, there are few classification proposals for the disease based on these examinations.
  
  
  METHODS
  A cross-sectional study was carried out, in which 41 non-smoking patients with IPF were evaluated. The following high resolution CT findings were quantified using a semi-quantitative scoring system: reticular abnormality, honeycombing and ground-glass opacity. The functional variables were measured by spirometry, forced oscillation technique, helium dilution method, as well as the single-breath method of diffusing capacity of carbon monoxide. With the interaction between functional indexes and high resolution CT scores through fuzzy logic, a classification for IPF has been built.
  
  
  RESULTS
  Out of 41 patients studied, 26 were male and 15 female, with a mean age of 70.8 years. Volume measurements were the variables which showed the best interaction with the disease extension on high resolution CT, while the forced vital capacity showed the lowest estimative errors in comparison to total lung capacity. A classification for IPF was suggested based on the 95% confidence interval of the forced vital capacity %: mild group (>92.7); moderately mild (76.9-92.6); moderate (64.3-76.8%); moderately severe (47.1-64.2); severe (24.3-47.0); and very severe (<24.3).
  
  
  CONCLUSIONS
  Through fuzzy logic, an IPF classification was built based on forced vital capacity measurement with a simple practical application.
authors.affiliation: Pulmonary Function Laboratory, State University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Agnaldo José
authors.initials: AJ
authors.lastname: Lopes
authors.forename: Domenico
authors.initials: D
authors.lastname: Capone
authors.forename: Roberto
authors.initials: R
authors.lastname: Mogami
authors.forename: Regina Serrão
authors.initials: RS
authors.lastname: Lanzillotti
authors.forename: Pedro Lopes de
authors.initials: PL
authors.lastname: Melo
authors.forename: José Manoel
authors.initials: JM
authors.lastname: Jansen
mesh_terms: D000368:Aged; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005260:Female; D017143:Fuzzy Logic; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000145:classification* / Q000000981:diagnostic imaging; D008168:Lung / Q000503:physiopathology; D008297:Male; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed