69: IL-6 and CH50 for monitoring of disease activity in systemic lupus erythematosus

Aims Low levels of complement 3 (C3) and 4 (C4) are known to be associated with disease activity in SLE. Recently automated IL-6 test is introduced to clinical laboratories. We aimed to determine the IL-6 and complements (C3, C4, and CH50) to find out the usefulness as monitoring markers for disease activity in SLE. Methods Eighty-seven SLE patients were studied. The patients were categorized as three groups according to the levels of C3 and C4; a group with normal C3 and C4 (37 patients), decreased C3 and normal C4 (38 patients) and decreased both C3 and C4 (12 patients). Plasma levels of IL-6 and CH50 were measured in those patients with additional healthy subjects. Kruskal–Wallis test was performed among the groups. Results Healthy subjects and the three groups (normal C3 and C4, decreased only C3, and decreased both complements) showed the median level of IL-6 less than 1.50, 2.74, 2.12, and 3.04 pg/mL; CH50 were 28.15, 18.65, 18.70, and 6.90 U/mL, respectively. Levels of IL-6 and CH50 showed no statistically significant differences among the patient subgroups. However, the data of all the SLE groups showed higher IL-6 ( p p  = 0.05). Conclusions In SLE patients, plasma IL-6 levels were significantly increased, and that of CH50 were declined in patients with both C3 and C4 decreased. IL-6 may be a useful marker for differentiation of SLE patients from healthy subjects. Further prospective studies on the usefulness of IL-6 are helpful for SLE disease activity.