title: Calprotectin (a major leucocyte protein) is strongly and independently correlated with joint inflammation and damage in rheumatoid arthritis.
abstract: OBJECTIVE
  Calprotectin is a major leucocyte protein, shown to correlate well with laboratory and clinical assessments in several inflammatory rheumatic diseases, and large concentrations of calprotectin have been found in synovial fluid from patients with rheumatoid arthritis (RA). The objective of the present study was to examine correlations between calprotectin and joint damage.
  
  
  METHODS
  145 patients with RA were analysed cross sectionally with laboratory (calprotectin, C reactive protein (CRP), and erythrocyte sedimentation rate (ESR)), clinical (28 joint counts (tender, swollen), physician global VAS, DAS28 and RA Articular Damage score (RAAD)), and radiographic (plain hand radiographs; modified Sharp's method) measurements, on the same day.
  
  
  RESULTS
  Calprotectin showed a highly significant correlation with measures of joint damage; modified Sharp score r = 0.43 (p<0.001) and RAAD r = 0.40 (p<0.001). The association with modified Sharp score and RAAD score was maintained after adjustment for CRP, ESR, rheumatoid factor, DAS28, sex, and age in a multiple regression analysis (p = 0.018 and p = 0.04, respectively), while neither CRP nor ESR showed any independent associations. Highly significant correlations (p<0.001) were also found between calprotectin and both laboratory and clinical markers of inflammation.
  
  
  CONCLUSIONS
  Calprotectin was found to significantly and independently explain the variation in the radiological and clinical assessments of joint damage. Longitudinal studies are required to examine whether calprotectin may predict the progression of joint damage in RA.
authors.affiliation: Department of Rheumatology, Diakonhjemmet Hospital, Box 23, Vinderen, N-0319 Oslo, Norway. h-hammer@diakonsyk.no
authors.forename: Hilde Berner
authors.initials: HB
authors.lastname: Hammer
authors.forename: Sigrid
authors.initials: S
authors.lastname: Odegard
authors.forename: Magne K
authors.initials: MK
authors.lastname: Fagerhol
authors.forename: Robert
authors.initials: R
authors.lastname: Landewé
authors.forename: Désirée
authors.initials: D
authors.lastname: van der Heijde
authors.forename: Till
authors.initials: T
authors.lastname: Uhlig
authors.forename: Petter
authors.initials: P
authors.lastname: Mowinckel
authors.forename: Tore K
authors.initials: TK
authors.lastname: Kvien
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000000981:diagnostic imaging; D001175:Arthrography; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D005500:Follow-Up Studies; D006225:Hand / Q000000981:diagnostic imaging; D006801:Humans; D007596:Joints / Q000276:immunology*; D039841:Leukocyte L1 Antigen Complex / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012217:Rheumatoid Factor / Q000032:analysis; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D039841:Leukocyte L1 Antigen Complex; D002097:C-Reactive Protein; D012217:Rheumatoid Factor