title: HLA-B27 homozygosity has no influence on radiographic damage in ankylosing spondylitis: Observation Study of Korean spondyloArthropathy Registry (OSKAR) data.
abstract: OBJECTIVE
  To evaluate the influence of homozygosity for HLA-B27 on the radiographic damage in ankylosing spondylitis (AS).
  
  
  METHODS
  A total of 368 AS patients with positive HLA-B27 status from the Observation Study of Korean spondyloArthropathy Registry (OSKAR) cohort were recruited for this study. HLA-B27 positive patients out of all AS patients were assessed for whether they had homozygosity or heterozygosity for HLA-B27. First, all data were stratified in relation to the carrier state of positive HLA-B27 for cross-sectional survey. Then we compared the radiographic damage score between groups. Second, we evaluated collected clinical and radiographic parameters at two different time points. Then we compared radiographic progression between groups. To use the mSASSS, cervical and lumbar spinal radiographs were examined by two experienced bone and joint radiologists (S. Lee, K.B. Joo).
  
  
  RESULTS
  The agreement between the two readers regarding mSASSS was very good: ICC coefficient 0.70 (95% CI 0.60-0.81). The mean age (SD) of the AS patients was 37.0 (9.2) years, and the mean disease duration (SD) was 15.6 (9.1) years. Of these patients, 34.5% (127 patients) had HLA-B27 homozygosity. The mean mSASSS unit (SEM) was not significantly different between groups (homozygosity 28.57±4.12 vs heterozygosity 23.34±3.44, P=0.344) on cross-sectional survey. When it comes to radiographic progression between groups over 5 years, there was no significant difference in spite of adjusting for confounding variable (homozygosity 4.98±0.98 vs heterozygosity 4.21±0.82, P=0.562).
  
  
  CONCLUSIONS
  The carrier state of positive HLA-B27 plays no role in determining the radiographic progression in AS.
authors: Department of Rheumatology, Chonnam National University Medical School and Hospital, Gwangju, Republic of Korea.
authors: Tae-Jong
authors: TJ
authors: Kim
authors: Il-Hoon
authors: IH
authors: Sung
authors: Seunghun
authors: S
authors: Lee
authors: Kyung Bin
authors: KB
authors: Joo
authors: Jung Hyun
authors: JH
authors: Choi
authors: Dong-Jin
authors: DJ
authors: Park
authors: Yong-Wook
authors: YW
authors: Park
authors: Shin-Seok
authors: SS
authors: Lee
authors: Tae-Hwan
authors: TH
authors: Kim
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D015796:HLA-B27 Antigen / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012042:Registries; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000000981:diagnostic imaging* / Q000235:genetics*
chemical_list: D015796:HLA-B27 Antigen
keywords: Ankylosing spondylitis; HLA-B27; Homozygosity; MSASSS