Measurement of plasma calprotectin as an indicator of arthritis and disease activity in patients with inflammatory rheumatic diseases.
OBJECTIVE
To investigate if the plasma level of the granulocyte protein calprotectin is a useful indicator of severity of arthritis in patients with inflammatory rheumatic diseases, and to analyze which factors contribute to the raised plasma calprotectin levels.


METHODS
Plasma calprotectin levels were measured by ELISA: In a cross sectional study of 154 patients with various inflammatory rheumatic diseases, calprotectin levels were correlated with laboratory and clinical variables.


RESULTS
The plasma levels of calprotectin and C-reactive protein (CRP) correlated significantly with the clinical evaluation of swollen joints (r = 0.51, p < or = 0.01 and r = 0.29, p < or = 0.01, respectively). Calprotectin levels, but not CRP levels or erythrocyte sedimentation rate, were significantly lower in patients with no swollen joints than in patients with one or more swollen joints (2613.6 micrograms/l vs 6287.0 micrograms/l, p < 0.001). A significant correlation between calprotectin and number of neutrophils was demonstrated (r = 0.43, p < or = 0.01), indicating that circulating neutrophils contribute to plasma calprotectin levels.


CONCLUSIONS
The plasma calprotectin level may be a useful indicator of arthritis in inflammatory rheumatic diseases.
Centre of Rheumatology, Haukeland University Hospital, Bergen, Norway.
J G
JG
Brun
R
R
Jonsson
H J
HJ
Haga
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001168:Arthritis / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood; D015415:Biomarkers; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000097:blood*; D015816:Cell Adhesion Molecules, Neuronal / Q000097:blood*; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D039841:Leukocyte L1 Antigen Complex; D008297:Male; D008875:Middle Aged; D009504:Neutrophils; D012216:Rheumatic Diseases / Q000097:blood*
D015415:Biomarkers; D002135:Calcium-Binding Proteins; D015816:Cell Adhesion Molecules, Neuronal; D039841:Leukocyte L1 Antigen Complex; D002097:C-Reactive Protein