title: Positive correlation between inflammation on sacroiliac joint MRI and serum C-terminal telopeptide of type-I collagen in ankylosing spondylitis but not in non-radiographic axial spondyloarthritis.
abstract: OBJECTIVE
  To identify the clinical disease activity scores and laboratory markers that best reflect magnetic resonance imaging (MRI)-determined sacroiliac joint (SIJ) inflammation in ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA).
  
  
  METHODS
  This cross-sectional study included all consecutive patients who presented with axial spondyloarthritis in 2013-2015. All underwent SIJ MRI. The bone marrow oedema in the inflammatory lesions on MRI was scored using the SPondyloArthritis Research Consortium of Canada (SPARCC) method. Bone-specific alkaline phosphatase (BALP), serum C-terminal telopeptide of type-I collagen (sCTX-I), and inflammatory markers were measured. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) were assessed. The correlations between the MRI-determined SIJ inflammation scores and disease activity scores and laboratory variables were evaluated.
  
  
  RESULTS
  Of the 81 patients with axSpA, 45 had AS and 36 had nr-axSpA. The AS and nr-axSpA groups did not differ in terms of disease activity scores, physical functional index, or MRI-determined SIJ inflammation. Erythrocyte sedimentation rate, C-reactive protein, and ASDAS correlated with MRI inflammatory scores in nr-axSpA but not in AS. sCTX-I correlated with MRI-determined SIJ inflammatory scores in AS only. BASDAI and BALP levels did not associate with MRI inflammatory scores in either group. Multivariate analysis showed that sCTX-I associated independently with MRI inflammatory score in AS (β=17.047, p=0.038).
  
  
  CONCLUSIONS
  Inflammatory markers and ASDAS correlated with active sacroiliitis on MRI in nr-axSpA only. In AS, only sCTX-I correlated with active inflammation on SIJ MRI. sCTX-I may be useful as a marker of objective inflammation in AS.
authors.affiliation: Div. of Rheumatology, Dept. of Internal Medicine, College of Medicine, The Catholic University of Korea; and Div. of Rheumatology, Dept. of Internal Medicine, Incheon Saint Mary's Hospital, The Catholic University of Korea, Incheon, Seoul, South Korea.
authors.forename: Kwi Young
authors.initials: KY
authors.lastname: Kang
authors.affiliation: Department of Radiology, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Joon-Yong
authors.initials: JY
authors.lastname: Jung
authors.affiliation: Div. of Rheumatology, Dept. of Internal Medicine, College of Medicine, The Catholic University of Korea; and Div. of Rheumatology, Dept. of Internal Medicine, Incheon Saint Mary's Hospital, The Catholic University of Korea, Incheon, Seoul, South Korea.
authors.forename: Yeon Sik
authors.initials: YS
authors.lastname: Hong
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Ji Hyeon
authors.initials: JH
authors.lastname: Ju
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, South Korea. rapark@catholic.ac.kr.
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Park
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood; D001853:Bone Marrow / Q000000981:diagnostic imaging; D001855:Bone Marrow Diseases / Q000000981:diagnostic imaging; D024042:Collagen Type I / Q000097:blood*; D003430:Cross-Sectional Studies; D004487:Edema / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000097:blood*; D011237:Predictive Value of Tests; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D058566:Sacroiliitis / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D055815:Young Adult
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D018836:Inflammation Mediators; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D000469:Alkaline Phosphatase