title: S100 proteins calprotectin and S100A12 are related to radiographic changes rather than disease activity in psoriatic arthritis with low disease activity.
abstract: OBJECTIVE
  To investigate serum levels of calprotectin (S100A8/S100A9) and S100A12 as markers of disease activity or distinct clinical or radiographic features in patients with psoriatic arthritis (PsA).
  
  
  METHODS
  Serum levels of calprotectin and S100A12, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were determined in 119 patients with PsA. Correlations to clinical variables were calculated, and subgroups of patients were compared.
  
  
  RESULTS
  The correlations to clinical disease activity measures were stronger for CRP than for ESR and calprotectin. In the regression analysis, calprotectin was identified as an independently associated factor for presence of peripheral radiographic features of arthritis (OR 1.33, 95% CI 1.01-1.76). S100A12 levels were also elevated in those with peripheral radiographic features (p = 0.036), but did not correlate with clinical variables of disease activity.
  
  
  CONCLUSIONS
  Calprotectin and S100A12 do not perform better than traditional biomarkers of disease activity in PsA, but were associated with presence of peripheral radiographic features in this cross-sectional study. The patients' low level of disease activity may have led to underestimation of the associations between any biomarker and disease measures.
authors.affiliation: Section for Rheumatology, Institute of Medicine, University of Bergen, Bergen, Norway. tor.madland@helse-bergen.no
authors.forename: Tor Magne
authors.initials: TM
authors.lastname: Madland
authors.forename: Annette
authors.initials: A
authors.lastname: Larsen
authors.forename: Johan G
authors.initials: JG
authors.lastname: Brun
mesh_terms: D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology; D015415:Biomarkers / Q000097:blood*; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D003430:Cross-Sectional Studies; D018450:Disease Progression; D006801:Humans; D039841:Leukocyte L1 Antigen Complex / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D009418:S100 Proteins / Q000097:blood*; D000067616:S100A12 Protein; D013223:Statistics as Topic