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.
Keywords: Cryoglobulinemia; disease activity index; systemic lupus erythematosus.