2016 Volume 65 Issue 5 Pages 551-556
Anti-Sm antibodies are specifically found in 5–30% of patients with systemic lupus erythematosus (SLE). The anti-Sm antibodies are directed against 7 proteins (BB’, D1, D2, D3, E, F, and G). These proteins constitute the common core of U1, U2, U4, and U5 small nuclear ribonucleoprotein (snRNP) particles. The Sm-BB’ proteins share cross-reactive epitopes with U1-RNP. Although SmB and SmD are the major targets of anti-Sm humoral autoimmunity, anti-SmD antibodies are considered to have the highest specificity for SLE. It has recently been shown that dimethylated arginine residues play an essential role in the formation of major SmD3 autoepitopes and that anti-SmD3 peptide antibodies are exclusively present in sera from SLE patients. The new kit Elia SmDp detects anti-Sm antibodies through the SmD3 synthetic peptide antigen. We evaluated the new kit with Phadia250. The CVs for within-run and between-day precisions ranged from 2.6 to 9.1%. The dilution linearity was maintained at 350 U/mL, and the detection limit was 0.1 U/mL. The concordance rate of positive and negative results was 95.5% between the new kit and the old kit Elia Sm. Therefore, the new kit is useful for a more accurate diagnosis.
