Analysis of serum anti-CCP antibodies. Patients with rhupus and those with rheumatoid arthritis (RA) had significantly higher serum antibodies against cyclic citrullinated peptides (anti-CCP antibodies) than patients with systemic lupus erythematosus (SLE) and healthy subjects (*p < 0.05). Results are expressed in U/ml for each patient. Horizontal lines indicate the median value for anti-CCP antibodies in each group. The dotted line represents the cutoff value for positivity (60 U/ml).