title: Clinical characteristics of nonradiographic axial spondyloarthritis in Korea: a comparison with ankylosing spondylitis.
abstract: OBJECTIVE
  To evaluate the clinical characteristics and outcomes of nonradiographic axial spondyloarthritis (nr-axSpA) in Korean patients.
  
  
  METHODS
  A retrospective analysis evaluated 155 patients with nr-axSpA at a single tertiary hospital between January 2001 and January 2011. Baseline characteristics and clinical courses were reviewed and compared with those of patients with ankylosing spondylitis (AS).
  
  
  RESULTS
  The mean age at disease onset was 29.5 ± 10.8 years and 52 (33.5%) patients were female. The mean age at symptom onset was older (29.5 ± 10.8 vs 25.9 ± 9.2, respectively, P < 0.001) and the male-to-female ratio was lower (2 : 1 vs 5 : 1, respectively, P = 0.001) in patients with nr-axSpA compared with patients with AS. The proportion of females was higher among patients with late onset SpA than early-onset nr-axSpA (55.0% vs 30.1%, respectively, P = 0.029). Among 74 patients with nr-axSpA, whose follow-up duration was more than 1.5 years, 29 (39.2%) patients progressed to AS during the follow-up period. The proportion of females was lower in progressors that that of non-progressors (13.8% vs 44.4%, respectively, P = 0.010). Presence of syndesmophyte and minimal X-ray changes at baseline were frequently observed in progressors compared with non-progressors (26.7% vs 0.0%, P = 0.006 and 69.0 vs 35.6%, P = 0.005, respectively).
  
  
  CONCLUSIONS
  The predominance of male patients is more prominent among Korean patients with SpA compared with Caucasians. Female nr-axSpA patients had late symptom onset and less progression to AS. X-ray changes at baseline were associated with radiographic progression.
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hyemin
authors.initials: H
authors.lastname: Jeong
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ji Y
authors.initials: JY
authors.lastname: Yoon
authors.affiliation: Department of Medicine, Jeju National University Hospital, Jeju, South Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Park
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Hwang
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hyungjin
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Medicine, Kangbook Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Joong K
authors.initials: JK
authors.lastname: Ahn
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jaejoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Koh
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hoon-Suk
authors.initials: HS
authors.lastname: Cha
mesh_terms: D000328:Adult; D017668:Age of Onset; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D011379:Prognosis; D011859:Radiography; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging; D017678:Sex Distribution; D012737:Sex Factors; D025241:Spondylarthritis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D013167:Spondylitis, Ankylosing / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D062606:Tertiary Care Centers; D013997:Time Factors; D055815:Young Adult
keywords: ankylosing spondylitis; clinical characteristics; non-radiographic axial spondyloarthritis