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

<jats:sec><jats:title>Objective</jats:title><jats:p>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).</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>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).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>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.</jats:p></jats:sec>