Serum cryoglobulins and disease activity in systematic lupus erythematosus

BACKGROUND To determine the prevalence of cryoglobulins in Iranian patients with systemic lupus erythematosus (SLE) and evaluate the correlation of cryoglobulins with disease activity in these patients. MATERIALS AND METHODS In a cross-sectional study, we investigated 80 consecutive women who fulfilled the 1982 revised criteria of the American College of Rheumatology for the classification of SLE. All the patients had undergone a medical interview and general physical examination by a rheumatologist for clinical and serologic characteristics of SLE. For the determination of cryoglobulins, sera were collected by a standard protocol at 37°C, and after incubation at 4°C for seven days, the level of cryoglobulins was estimated for each patient. RESULTS Cryoglobulins were detected in the sera of 39 (48.8%) patients. All of these patients had cryocrit over 5%. Disease was active in 30 patients [SLEDAI ≥6 (DAI: disease activity index)] and inactive in 50 (SLEDAI <6). There was no significant difference between active and inactive patients for the presence of serum cryoglobulins (r = 0.086, P = 0.56). A significant positive correlation was observed between antinuclear antibody (ANA), anti-dsDNA (dsDNA: Double-stranded deoxyribonucleic acid), CH50 (CH50: total hemolytic complement assay), and C-reactive protein (CRP) (r = 0.21, P = 0.004, r = 0.65, P = 0.001, r = 0.45, P = 0.023, r = 0.38, P = 0.036, respectively). Hepatitis C virus (HCV) infection was not detected in any of the SLE patients. CONCLUSION Although the presence of cryoglobulins in the SLE patients correlated with positive anti-ds DNA and low CH50, it could not be predict activity of the disease.