Anti-ribosomal P protein IgG autoantibodies in patients with systemic lupus erythematosus: diagnostic performance and clinical profile

Abstract

BackgroundThis study was devised to assess the performance of anti-ribosomal P (anti-Rib-P) antibodies in the diagnosis of systemic lupus erythematosus (SLE) and the association of these antibodies with the clinical features of SLE.MethodsWe used a fluorescence enzyme immunoassay to determine anti-Rib-P levels in an SLE group, a rheumatic disease control (RDC) group (rheumatoid arthritis (RA), ankylosing spondylitis, psoriatic arthritis and juvenile idiopathic arthritis), and a healthy control (HC) group. We also determined anti-Smith antigen (anti-Sm) and anti-double-stranded DNA (anti-dsDNA) antibody levels. Receiver operating characteristic (ROC) curves were constructed and the best cut-off points for positivity were determined. Using regression analysis, the relationship between clinical variables and autoantibody levels was analyzed.ResultsIn total, 127 patients with SLE, 256 controls with other rheumatic diseases, and 100 HCs were studied. Anti-Rib-P autoantibodies were positive in 18 (14.2%) of the patients with SLE (mean concentration of 30.6 ± 46.9 U/ml) and in 2 patients with RA (0.8% of the RDC group). In addition, 12 patients with SLE (9.4%) were positive for anti-Sm (31.1 ± 40.8 U/ml) and 63 (49.6%) were positive for anti-dsDNA autoantibodies (88.4 ± 88.5 U/ml). When we assessed the 18 patients with SLE who had tested positive for anti-Rib-P, we found that 4 of these were positive for anti-Rib-P only, whereas 12 were positive for anti-Rib-P plus anti-dsDNA, and 2 were positive for all three antibodies. There were no samples positive for anti-Rib-P plus anti-Sm. The specificity, sensitivity, positive likelihood ratio, and negative likelihood ratio of anti-Rib-P for SLE diagnosis were 99.4%, 14.2%, 23.7%, and 0.86%, respectively.Caucasian ethnicity was associated with lower anti-Rib-P antibody levels. No relation was found between anti-Rib-P levels and neuropsychiatric or other clinical features.ConclusionsAnti-Rib-P autoantibodies have high specificity for SLE, and measurement of these might improve the accuracy of SLE diagnosis. In this study, we found that Caucasian ethnicity was associated with lower anti-Rib-P antibody levels.

Neuropsychiatric lupus: a mosaic of clinical presentations

“…Nevertheless, other reports have failed to confirm this relationship [12]. A recent meta-analysis suggested that anti-ribosomal-P antibodies are specifically related to psychosis in NPSLE [10].…”

Novel pebbles in the mosaic of autoimmunity

“…Carmona-Fernandes et al . [30] found that the specificity, sensitivity, positive predictive value, and negative predictive value of anti-Rib-P for SLE diagnosis were 99.4%, 14.2%, 90%, and 76.4%, respectively. Although, anti-Rib-P was not clearly associated with any clinical condition, including NPSLE, in that study, nonetheless, the effects of these autoantibodies on the CNS have been addressed in several other studies.…”

Systemic Lupus Erythematosus with Neuromyelitis Optica

“…It has been shown that antiphospholipid antibodies including anti-cardiolipin and lupus anti-coagulant are some of the strongest NPSLE-related factors expressed especially in relation to cerebrovascular disease [4,5]. One study also reported anti-ribosomal P antibodies as risk factors for SLE psychosis [6]; however, this is inconclusive since another report showed no relation between these antibodies and neuropsychiatric illness [7]. Moreover, anti-double stranded DNA antibodies (anti-dsDNA), which are the most represented autoantibodies in SLE, are reported to cross-react with NR2A and NR2B subunits of the N-methyl-d-aspartate receptor (NMDAR) [8,9].…”