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Anti-Rib-P autoantibodies might be useful for SLE diagnosis
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Anti-ribosomal P autoantibodies had a high specificity for systemic lupus erythematosus, and their measurement might improve disease diagnosis, according to study results.
Researchers in Portugal used fluorescence enzyme immunoassay to determine anti-ribosomal P (anti-Rib-P) levels in serum samples collected between May 2007 and December 2009. Study groups included 127 patients with systemic lupus erythematosus (SLE), 256 patients in a rheumatic disease control (RDC) group (100 rheumatoid arthritis [RA], 99 ankylosing spondylitis, 34 juvenile idiopathic arthritis and 23 psoriatic arthritis) and 100 healthy controls. Anti-Smith antigen (anti-Sm) and anti-double-stranded DNA (anti-dsDNA) antibody levels also were determined.
Optimal cutoff points for positivity were determined after construction of receiver operating characteristics. The relationship between clinical variables and autoantibody levels was assessed though regression analysis.
Eighteen SLE patients (14.2%) had positive anti-Rib-P autoantibodies (mean concentration of 30.6 ± 46.9 U/mL), as did two patients with RA (0.8% of the RDC group). In the SLE group, 12 patients (9.4%) tested positive for anti-Sm (31.1 ± 40.8 U/mL) and 63 patients (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 four of these were positive for anti-Rib-P only, whereas 12 were positive for anti-Rib-P plus anti-dsDNA, and two were positive for all three antibodies,” the researchers reported. “There were no samples positive for anti-Rib-P plus anti-Sm.”
There was a 99.4% specificity, 14.2% sensitivity, 23.7% positive likelihood ratio and 0.86% negative likelihood ratio of anti-Rib-P for diagnosing SLE. Lower anti-Rib-P antibody levels were associated with Caucasian ethnicity. Anti-Rib-P levels and neuropsychiatric or other clinical features indicated no relationship.
“The presence of anti-Rib-P antibodies in patients negative for anti-DNA and anti-Sm indicates that these autoantibodies might be useful for SLE diagnosis,” the researchers concluded. “We propose that further studies should be performed to evaluate the relevance of anti-Rib-P antibody testing for SLE diagnosis.”
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