Usefulness of soluble CD163 as a biomarker for macrophage activation syndrome associated with systemic lupus erythematosus.

Objective: We aimed to study the usefulness of serum soluble CD163 (sCD163) as a biomarker for macrophage activation syndrome (MAS) associated with systemic lupus erythematosus (SLE).

Methods: Serum sCD163 levels were retrospectively measured by enzyme-linked immunosorbent assay for SLE patients associated with MAS (SLE-MAS), lupus nephritis (LN), or autoimmune hemolytic anemia (AIHA) and/or immune thrombocytopenia (ITP) and healthy controls (HCs). Posttreatment samples were also evaluated in the available SLE-MAS patients. The associations between serum sCD163 levels and clinical information were statistically analyzed.

Results: The serum sCD163 levels in SLE-MAS, LN and SLE-AIHA/ITP groups were significantly higher than those in HCs (n = 17, 29, 13, and 68, respectively; p < 0.01 for all comparisons). In addition, the serum sCD163 levels in the SLE-MAS group were even higher than those in the LN and SLE-AIHA/ITP groups (p < 0.01 for both comparisons). Serum sCD163 levels were correlated with the SLE Disease Activity Index 2000 scores (r = 0.53), whereas they were not correlated with the serum ferritin levels. With the determined cut-off value, the sensitivity and specificity of serum sCD163 for the diagnosis of SLE-MAS were 59% and 86%, respectively. Retesting showed that the serum sCD163 levels decreased significantly following treatment in parallel with disease amelioration in the SLE-MAS group (p < 0.01).

Conclusions: The present study suggests the usefulness of serum sCD163 as a diagnostic and disease-activity biomarker for SLE-associated MAS. Serum sCD163 might also have a different role as a biomarker for SLE-associated MAS than serum ferritin does.