Abstract
Background Neuropsychiatric (NP) involvement and fatigue are major problems in systemic lupus erythematosus (SLE). S100A8/A9 is a marker of inflammation and responds to therapy in SLE patients. S100A8/A9 has an immunopathogenic role in various neurological diseases. We investigated S100A8/A9 in relation to NP-involvement and fatigue in SLE. Methods 72 consecutive SLE outpatients at a tertiary centre and 26 healthy controls were included in this cross-sectional study. NPSLE was determined by specialists in rheumatology and neurology and defined according to three attribution models: “ACR”, “SLICC A” and “SLICC B”. Cerebral MRI was assessed by a neuroradiologist and neurocognitive testing by a neuropsychologist. The individuals were assessed by scores of pain (VAS), fatigue (VAS and FSS), depression (MADRS-S), and health-related life quality (EQ5D). Concentrations of S100A8/A9 in serum and cerebrospinal fluid were measured with ELISA. Statistical calculations were performed using non-parametric methods. Results Serum concentrations of S100A8/A9 were higher in NPSLE patients compared with non-NPSLE patients when applying the ACR and SLICC A models, but not significant when applying the SLICC B model (medians 1400 ng/ml; 920 ng/ml, p=0.011; 1560 ng/ml; 1090 ng/ml, p=0.050; 1460 ng/ml; 1090 ng/ml, p=0.083, respectively). The concentrations were higher in SLE patients compared with controls (medians 1230 ng/ml; 790 ng/ml, p=0.023). No differences of CSF S100A8/A9 concentrations were observed between NPSLE and non-NPSLE patients. SLE patients with depression or cognitive dysfunction as an ACR NPSLE manifestation had higher serum S100A8/A9 concentrations than non-NPSLE patients (median 1460 ng/ml, p=0.007 and 1380 ng/ml, p=0.013, respectively). Higher serum S100A8/A9 correlated with higher VAS fatigue (r=0.31; p=0.008), VAS pain (r=0.27, p=0.021), and lower EQ5D (r=-0.29, p=0.014) in SLE patients. NPSLE was associated with higher plasma CRP concentrations, higher scores of fatigue and pain, lower EQ5D, and fewer weekly work hours. Serum S100A8/A9 was not independently associated with NPSLE when adjusting for plasma CRP, and scores of fatigue (FSS) and pain (VAS), (OR 1.70, 95% CI 0.82-3.53, p=0.15). Conclusions Serum S100A8/A9 concentrations may be associated with NPSLE and fatigue. S100A8/A9 may be of interest in evaluating NPSLE, although further investigations are needed.