Calprotectin (a major leukocyte protein) is strongly and independently correlated to joint inflammation and damage in rheumatoid arthritis

Sigrid degård ¹,

¹ Diakonhjemmet Hospital, Norway
² Ullevål Hospital, Norway
³ University Hospital Maastricht, Netherlands

^* To whom correspondence should be addressed. E-mail: h-hammer{at}diakonsyk.no.

Accepted 21 December 2006

	Abstract

Objective: Calprotectin is a major leukocyte protein, shown to correlate well with laboratory and clinical assessments in several inflammatory rheumatic diseases, and high amounts 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: A total of 145 patients with RA were analysed cross-sectionally with laboratory (calprotectin, CRP and 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, at 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 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.

Conclusion: 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.

Keywords: calprotectin, joint damage, joint inflammation, radiographs, rheumatoid arthritis

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