Objectives: To identify specific cerebrospinal fluid (CSF) biomarkers for the diagnosis and disease severity evaluation of neuropsychiatric systemic lupus erythematosus (NPSLE).
Methods: Patients presented with neuropsychiatric symptoms were recruited and categorised as 36 NPSLE, 19 SLE controls, 4 other connective tissue disease (CTD) controls and 10 nervous system disorder (NSD) controls. The NPSLE group consisted of severe NPSLE (sNPSLE) and mild NPSLE (mNPSLE). Potential biomarkers were determined by Luminex multiplex assay and enzyme-linked immunosorbent assay.
Results: 1) Among a variety of neurological disease-related proteins, only ubiquitin carboxyl hydrolase L1 (UCH-L1) levels were significantly elevated in the CSF samples of sNPSLE patients compared with those of mNPSLE patients (p=0.020) and SLE controls (p=0.037). CSF UCH-L1 levels were significantly positively correlated with SLE disease activity index and overlap number of NPSLE manifestations. 2) CSF anti-UCH-L1 autoantibodies were significantly elevated in patients with NPSLE in comparison to all of the control groups, with a sensitivity of 53% and a specificity of 91% for NPSLE. CSF anti-UCH-L1 levels were associated with organ involvement and were positively correlated with serum anti-UCH-L1 levels in the NPSLE patients (r=0.4551, p=0.0382).
Conclusions: Anti-UCH-L1 is a promising CSF biomarker for NPSLE diagnosis with high specificity, and the elevated levels of CSF UCH-L1 reflect the clinical severity of NPSLE. The elevation of UCH-L1 and its autoantibody in NPSLE patients showed us novel aetiological insights on NPSLE.