title: HLA class II is associated with distal interphalangeal osteoarthritis.
abstract: OBJECTIVE
  To investigate whether there is an association between HLA class II and distal interphalangeal osteoarthritis (DIP OA).
  
  
  METHODS
  The study group consisted of consecutive patients with and without DIP OA aged between 40 and 70 years. DIP OA was diagnosed by radiology. These patients were referred to an "Early Arthritis Clinic" (EAC) with different types of arthritis at an early stage. Patients with rheumatoid arthritis, systemic lupus erythematosus, spondyloarthropathies, and psoriatic arthritis were excluded for the purpose of this study. DNA typing for HLA-DR and x ray examination of the hands were performed at enrollment in the EAC. To establish whether the study group was representative of the Dutch population, a population based study in Zoetermeer (n=3243) for the prevalence of DIP OA and blood donors in the Leiden area (n=2400) for the HLA-DR antigen frequencies were used as references.
  
  
  RESULTS
  Fifty five patients (33%) of the total study group (n=166) had DIP OA. The prevalence of DIP OA and frequency of the HLA-DR alleles were similar to those of the two reference groups. Within the study group an association between DIP OA and HLA-DR2 and DR4 with respectively odds ratios of 2.4 (95% confidence interval (CI) 1.1 to 5.0) and 0.3 (95% CI 0.1 to 0.7) was found. No association was found between other HLA-DR alleles and DIP OA.
  
  
  CONCLUSIONS
  The study group is a representative sample of the Dutch population. The HLA-DR2 allele was more common in patients with DIP OA. Furthermore, an inverse relation was observed between DIP OA and HLA-DR4. The results confirm findings from other investigations implicating HLA-DR2 as a risk factor in the development of DIP OA.
authors.affiliation: Department of Rheumatology, Leiden University Medical Centre, the Netherlands. N.Riyazi@lumc.nl
authors.forename: N
authors.initials: N
authors.lastname: Riyazi
authors.forename: J
authors.initials: J
authors.lastname: Spee
authors.forename: T W J
authors.initials: TW
authors.lastname: Huizinga
authors.forename: G M T
authors.initials: GM
authors.lastname: Schreuder
authors.forename: R R P
authors.initials: RR
authors.lastname: de Vries
authors.forename: F W
authors.initials: FW
authors.lastname: Dekker
authors.forename: M
authors.initials: M
authors.lastname: Kloppenburg
mesh_terms: D000328:Adult; D000368:Aged; D000483:Alleles; D005260:Female; D005384:Finger Joint / Q000000981:diagnostic imaging; D005802:Genes, MHC Class II; D015802:HLA-DR2 Antigen / Q000032:analysis; D015804:HLA-DR4 Antigen / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D016017:Odds Ratio; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000235:genetics*; D015995:Prevalence; D011446:Prospective Studies; D011859:Radiography
chemical_list: D015802:HLA-DR2 Antigen; D015804:HLA-DR4 Antigen