title: Subtyping of juvenile idiopathic arthritis using latent class analysis. British Paediatric Rheumatology Group.
abstract: OBJECTIVE
  To use statistical techniques to identify underlying subtypes of juvenile idiopathic arthritis (JIA) that best explain the observed relationships of clinical and laboratory variables, and to compare the statistically derived subtypes with those defined by the International League of Associations for Rheumatology (ILAR) criteria and examine them for HLA associations.
  
  
  METHODS
  Information on 572 patients diagnosed as having JIA was summarized by 10 clinical and laboratory categorical variables (age at onset, large joint involvement, small joint involvement, polyarthritis, symmetric arthritis, spinal pain, fever, psoriasis, antinuclear antibodies [ANA], and rheumatoid factor). Latent class analysis (LCA) was used to identify underlying ("latent") classes that explained the relationships among the observed variables. Statistical models incorporating 5-8 latent classes were applied to the data.
  
  
  RESULTS
  The 7-class model was the most appropriate. Patterns of joint involvement and the presence of ANA were influential in determining latent classes. There was some correspondence between the latent classes and the ILAR categories, but they did not coincide completely. Significant differences between the latent classes were seen for 3 HLA haplotypes (DRB1*04-DQA1*03-DQB1*03, DRB1*13-DQA1*01-DQB1*06, and DRB1*08-DQA1*0401-DQB1*0402).
  
  
  CONCLUSIONS
  LCA provides a novel approach to the task of identifying homogeneous subtypes within the umbrella of JIA. In further work, the identified latent classes will be examined for associations with other candidate genes and for differences in outcome.
authors.affiliation: ARC Epidemiology Unit, University of Manchester, UK.
authors.forename: E
authors.initials: E
authors.lastname: Thomas
authors.forename: J H
authors.initials: JH
authors.lastname: Barrett
authors.forename: R P
authors.initials: RP
authors.lastname: Donn
authors.forename: W
authors.initials: W
authors.lastname: Thomson
authors.forename: T R
authors.initials: TR
authors.lastname: Southwood
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000145:classification* / Q000473:pathology / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D005163:Factor Analysis, Statistical; D005260:Female; D006239:Haplotypes; D006801:Humans; D007596:Joints / Q000473:pathology / Q000503:physiopathology; D008297:Male; D015233:Models, Statistical; D016017:Odds Ratio; D011237:Predictive Value of Tests