Abstract: A method and assay kit are provided for diagnosing systemic lupus erythematosus by detecting a concentration of anti-EF-1.alpha. antibodies that may be found within a sample of body fluid. The assay employs substantially pure EF-1.alpha. antigen, which is preferably bound to a polystyrene support, and an indicator reagent for detecting and quantifying a quantity of anti-EF-1.alpha. antibody that attaches to the bound antigen. The support and bound antigen are contacted with the fluid sample to allow the formation of an antigen/antibody complex between the support-bound EF-1.alpha. antigen and the anti-EF-1.alpha. antibody. The urine-sample assay has a sensitivity for active SLE of at least about 90%, and a specificity of about 90%.

Abstract: Assays which aid in diagnosing systemic lupus erythematosus and rheumatoid arthritis are disclosed. One assay tests urine samples for the presence or absence of an RNA polymerase I antibody which specifically binds with RNA polymerase I antigen and another assay tests for the presence or absence of an RNA polymerase I antigen that specifically binds with an antibody to RNA polymerase I.

Abstract: A method is described for the differential diagnosis of rheumatological diseases. Sera from patients with SLE; MCTD, and RA are screened for antibodies directed against RNA polymerase II using a solid phase immunoassay. Significant levels of the antibodies were detected with sera of all SLE and MCTD patients and in 78% of the RA patients. No detectable anti-RNA polymerase I antibodies were detected in the sera of healthy individuals.Sera from patients with SLE contained immunoglobulins directed against the S3 subunit of RNA polymerase I, as well as antibodies to the S2 or S5 subunits, RA patient's sera contained antibodies only to S3 while MCTD patients sera contained antibody to S4 in addition to antibody to the S3 and S5 subunits. The identification of specific reaction patterns of the antibodies with the individual subunits of the RNA polymerase I is indicative of a particular class of rheumatological disease.