BackgroundThis study aimed to evaluate autoantibodies against the native ribosomal P complex (anti‐Rib‐PC) and recombinant ribosomal P proteins (anti‐Rib‐P0, anti‐Rib‐P1, anti‐Rib‐P2) for their prevalence, diagnostic relevance and clinical associations in a Chinese cohort with systemic lupus erythematosus (SLE).MethodsAnti‐Rib‐P, anti‐dsDNA and anti‐Smith antigen (Sm) antibodies were analyzed in sera from 198 patients with SLE, 33 with rheumatoid arthritis, 61 with Sjögren's syndrome and 70 healthy individuals by means of ELISA.ResultsAntibody prevalences were 29.8% (anti‐Rib‐PC), 33.3% (anti‐Rib‐P0), 42.9% (anti‐Rib‐P1) and 34.3% (anti‐Rib‐P2), at a specificity of 99%. Among SLE patients lacking anti‐dsDNA and anti‐Sm, 27.8% showed positive for at least one of the investigated anti‐Rib‐P types. The serological hit rate provided by anti‐dsDNA/anti‐Sm detection (72.7%) was increased upon parallel testing for anti‐Rib‐PC (77.3%) or anti‐Rib‐P0/P1/P2 (80.3%). Anti‐Rib‐P positivity was associated with disease activity, neuropsychiatric events, lupus nephritis, skin rash, lymphocytopenia, increased erythrocyte sedimentation rates, decreased complement C3/C4 and elevated IgA/IgG levels.ConclusionBased on these results, antibodies against ribosomal P proteins are important complementary parameters to anti‐dsDNA and anti‐Sm, and should be considered for inclusion in the classification criteria for SLE. The diagnostic value of anti‐Rib‐P0/P1/P2 is diagnostically superior to that of anti‐Rib‐PC. J. Clin. Lab. Anal. 27:87–95, 2013. © 2013 Wiley Periodicals, Inc.