Background Neuropsychiatric systemic lupus erythematosus (NPSLE) is one of the most serious complications of systemic lupus erythematosus (SLE), lacking efficient diagnostic biomarkers. Previous studies have shown that anti-ubiquitin carboxyl hydrolase L1(UCH-L1) autoantibody is a promising cerebrospinal fluid (CSF) biomarker for NPSLE diagnosis. The purpose of this study is to explore the serum autoantibodies against different UCH-L1 epitopes and investigate the potential diagnostic value of serum autoantibodies against different UCH-L1 epitopes in NPSLE.

Methods The epitopes of UCH-L1 protein were predicted in DNAStar software. The serum levels of different UCH-L1 epitope autoantibodies in 40 NPSLE patients, 32 SLE patients without neuropsychiatric symptoms and 21 healthy controls were determined by enzyme-linked immunosorbent assay (ELISA). Data were analysed using Pearson correlation analysis, ROC curve analysis, nonparametric Mann-Whitney test, t-test and χ2 test.

Results We screened three candidate epitopes of UCH-L1 protein. The autoantibody against amino acid 58 to 69 of UCH-L1 (UCH58-69) showed highest diagnostic power in distinguishing NPSLE patients from SLE patients without neuropsychiatric symptoms (p=0.0038). The ROC analysis showed that the specificity and sensitivity of anti-UCH58-69 were 92.3% and 37.5%, respectively. In addition, increased serum anti-UCH58-69 levels were associated with increased SLEDAI, CSF microprotein, CSF leukocyte count, ESR, AnuA, anti-dsDNA, IgG and IgM but with decrease of C3 in SLE patients.

Conclusions The serum levels of anti-UCH58-69 significantly increased in NPSLE patients compared with SLE patients without neuropsychiatric symptoms and were correlated with disease severity. Anti-UCH58-69 autoantibody may become a novel serum biomarker for NPSLE non-invasive diagnosis, which might be applicable for NPSLE early screening and diagnosis.