Levels of Acute-phase-reactants in Patient with Dermatomysitis and Its Correlations with IL-6 and Dermatomyositis Disease Activity

Objective To determine the association between acute-phase-reactants (APR) and interleukin-6 (IL-6) in patient with dermatomysitis (DM). Methods The levels of C-reactive protein (CRP), serum amyloid A protein (SAA) and serum ferritin (SF) in peripheral blood of 31 adult DM patients were determined by chemiluminescence immunoassay, and compared with those of 23 patients with systemic lupus erythematosus (SLE), 22 patients with rheumatoid arthritis (RA), and 18 patients with Sjögren syndrome (SS). The correlations between the levels of those APR and IL-6 were examined. We also measured dermatomyositis disease activity using myositis disease activity assessment tool (MDAAT), and examined its association with APR levels. Results DM patients had significantly lower level of CRP(17.08±17.18)mg/L than those patients with RA(85.95±60.62)mg/L, P<0.000 1, SLE(51.34±52.98)mg/L, P=0.006 and SS(47.00±47.24) mg/L, P=0.018. DM patients had significantly lower level of SAA(92.04±98.93) mg/L than those patients with RA(311.30±292.45) mg/L, P=0.002 and SS(284.31±325.30) mg/L, P=0.025. DM patients had significantly higher level of SF(510.10±610.73)ng/mL than those patients with SS(220.33±164.07) ng/mL, P=0.02, as well as those with RA and SLE albeit without statistical significance. All of the three APRs were positive correlated with IL-6 level. No significant associations between APR and systemic or global disease activities were found, although CRP was associated with constitutional disease activity and SF was associated with pulmonary disease activity. Conclusion DM patients have lower levels of elevated APR than the other three common connective tissue diseases, which is associated with IL-6 but not with global disease activity.