Measuring serum levels of high-mobility group box 1 by enzyme-linked immunosorbent assay does not identify bacterial infections in patients with systemic lupus erythematosus.

Introduction: studies have shown that high-mobility group box 1 (HMGB1) may play a role in the propagation of inflammatory response in infectious and autoimmune diseases. However, its utility in the differentiation between infections and disease flares in systemic lupus erythematosus (SLE) patients has not been investigated.
Methods: we prospectively recruited 38 hospitalized patients from Taiwan with SLE. Among them, 13 patients suffered from superimposed bacterial infections while the other 25 patients experienced disease flares. SLE disease activity was assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Serum levels of HMGB1 were measured by an enzyme-linked immunosorbent assay (ELISA). Additionally, serum levels of high-sensitivity C-reactive protein (hsCRP) were determined among 34 of the SLE patients.
Results: there was no significant difference between the serum HMGB1 levels in SLE patients with disease flares and patients with bacterial infections. Among SLE patients with disease flares, serum HMGB1 levels were significantly higher in patients with mild to moderate flares (3.53 ng/ml) compared to those with severe flares (1.72 ng/ml, p < 0.05). For identifying bacterial infections in patients with SLE, the area under the receiver operating characteristic (ROC) curve was 0.705 (95% CI: 0.524-0.848) for hsCRP and 0.497 (95% CI: 0.331-0.663) for HMGB1. The best cutoff value for hsCRP was 1.07 mg/dl for detection of bacterial infections in SLE patients, with a sensitivity of 75% and a specificity of 68%.
Conclusion: the determination of serum HMGB1 level is not useful in the differentiation between disease flares and bacterial infections in SLE patients.
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