Graphs showing levels of antiribosomal P protein antibodies in SLE, other rheumatic diseases and healthy donors. Autoantibodies directed against (a) native ribosomal P heterocomplex (aRibPNH), (b) recombinant ribosomal P0 protein (aRibPR0), (c) recombinant ribosomal P1 (aRibPR1) and (d) recombinant ribosomal P2 protein (aRibPR2) were measured using enzyme-linked immunosorbent assay. Dotted lines represent the distinct cut-offs based on ROC curve analysis at specificities of 95% (dotted line), 98% (broken line) and 99% (dotted and broken line). Values >30 RU/ml were set to 30 RU/ml for clearer arrangement of the figures. SLE, systemic lupus erythematosus; SSc, systemic sclerosis; pSS, primary Sjögren's syndrome; RA, rheumatoid arthritis; HD, healthy donors. RU, relative units.