Additional diagnostic benefit of antiribosomal P protein antibodies in lupus patients. Both flow charts aim to demonstrate the additional diagnostic value of antiribosomal P protein antibodies (anti-RibP) in the absence of anti-double-stranded DNA (anti-dsDNA) and anti-Smith (anti-Sm) antibodies for lupus diagnostics. The cutoffs of all test systems were set to ensure an absolute specificity of 100% (see Table 1 for cutoffs). Anti-dsDNA and anti-Sm antibodies were selected because they are highly specific for systemic lupus erythematosus (SLE) (instead of, for example, anti-phospholipid antibodies) and are part of American College of Rheumatology classification criteria for SLE . Flowcharts differ only in the test system used for the detection of anti-dsDNA antibodies. (A) Anti-dsDNA enzyme-linked immunosorbent assay (ELISA) and (B) Farr assay. RibPNH+, native ribosomal P heterocomplex-positive; RibPR0+, recombinant ribosomal P0 protein-positive; RibPR1+, recombinant ribosomal P1 protein-positive; RibPR2+, recombinant ribosomal P2 protein-positive.