title: Serum inflammatory biomarkers fail to identify early axial spondyloarthritis: results from the SpondyloArthritis Caught Early (SPACE) cohort.
abstract: BACKGROUND
  Decreasing the diagnostic delay in axial spondyloarthritis (axSpA) remains a major challenge. Here, we assessed the value of serum inflammatory biomarkers to distinguish early axSpA from other pathologies in a large cohort of patients referred with early back pain.
  
  
  METHODS
  Serum c reactive protein (CRP), erythrocyte sedimentation rate (ESR) and calprotectin were determined in the SPondyloArthritis Caught Early (SPACE) cohort (n=310), an early back pain inception cohort. Additionally, explorative serum biomarkers derived from the literature (interleukin-27 (IL-27), human β-defensin-2 (hBD-2) and lipcolin-2 (LCN-2)) were determined by ELISA in full-blown patients with ankylosing spondylitis (AS) (n=21) and healthy controls (n=20).
  
  
  RESULTS
  Serum CRP and ESR levels were not elevated in early axSpA versus 'control' back pain patients. Serum calprotectin was elevated in early axSpA versus controls (p=0.01) but failed to identify early axSpA at the individual level (positive predictive value of 38.7%). As to explorative biomarkers, serum levels of IL-27 were not detectable, and hBD-2 and LCN-2 serum levels were not elevated in full-blown AS versus healthy controls (p=0.572, p=0.562, respectively). Therefore, these markers were not further determined in the SPACE cohort.
  
  
  CONCLUSIONS
  None of the candidate serum inflammatory markers were useful as diagnostic markers in the early phase of axSpA.
authors.affiliation: Department of Clinical Immunology and Rheumatology , Amsterdam Rheumatology and Immunology Center, Academic Medical Center/University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: Maureen C
authors.initials: MC
authors.lastname: Turina
authors.affiliation: Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology and Immunology Center, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands; Department of Experimental Immunology, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Yeremenko
authors.affiliation: Department of Rheumatology , Leiden University Medical Center , Leiden , The Netherlands.
authors.forename: Floris
authors.initials: F
authors.lastname: van Gaalen
authors.affiliation: Department of Rheumatology , Groene Hart Ziekenhuis , Gouda , The Netherlands.
authors.forename: Maikel
authors.initials: M
authors.lastname: van Oosterhout
authors.affiliation: Department of Rheumatology , Diakonhjemmet Hospital , Oslo , Norway.
authors.forename: Inger J
authors.initials: IJ
authors.lastname: Berg
authors.affiliation: Rheumatology Unit, Department of Medicine DIMED , University of Padova , Padova , Italy.
authors.forename: Ramona
authors.initials: R
authors.lastname: Ramonda
authors.affiliation: Department of Experimental Immunology , Academic Medical Center/University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: Cristina M C
authors.initials: CM
authors.lastname: Lebre
authors.affiliation: Department of Clinical Immunology and Rheumatology , Amsterdam Rheumatology and Immunology Center, Academic Medical Center/University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Landewé
authors.affiliation: Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology and Immunology Center, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands; Department of Experimental Immunology, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Dominique
authors.initials: D
authors.lastname: Baeten
keywords: Inflammation; Low Back Pain; Spondyloarthritis