Calprotectin (a major leucocyte protein) is strongly and independently correlated with joint inflammation and damage in rheumatoid arthritis.
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.
Hammer
Hilde Berner
HB
Department of Rheumatology, Diakonhjemmet Hospital, Box 23, Vinderen, N-0319 Oslo, Norway. h-hammer@diakonsyk.no
Odegard
Sigrid
S
Fagerhol
Magne K
MK
Landewé
Robert
R
van der Heijde
Désirée
D
Uhlig
Till
T
Mowinckel
Petter
P
Kvien
Tore K
TK
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
D015415:Biomarkers; D039841:Leukocyte L1 Antigen Complex; D002097:C-Reactive Protein; D012217:Rheumatoid Factor