title: Anti-RNA polymerase III antibodies in patients with systemic sclerosis detected by indirect immunofluorescence and ELISA.
abstract: OBJECTIVE
  To evaluate the analytical performance of an ELISA for the detection of anti-RNA polymerase III antibody (ARA) and to assess IIF as a method for identifying this antibody.
  
  
  METHODS
  A commercially available ELISA was used to assess the presence of ARA in sera from 1018 SSc patients. The sera had been divided into sub-populations based on the presence of specific autoantibodies, ANA pattern or the absence of both. Patients with ARA (n = 209) had been identified by characteristic ANA pattern by IIF on HEp-2 cell substrate [and additionally by radio-immunoprecipitation (IP) in 157/209 cases]. The remaining 809 SSc patients acted as a control group.
  
  
  RESULTS
  Of 157 patients in whom ARA had been confirmed by IP, 150 were positive by ELISA providing a sensitivity of 96%. In the group where ARA had only been assessed by IIF, 100% (52/52) were ELISA positive. The ANA patterns indicating the presence of ARA were a fine-speckled nucleoplasmic stain with additional occasional bright dots, with or without concurrent punctate nucleolar staining. In the SSc control group, the ELISA attained a specificity of 98%, ARA being detected in 17/809 patients.
  
  
  CONCLUSIONS
  We report the outcome of a study on a large population of SSc patients that shows the ARA ELISA to be of high analytical sensitivity and specificity. We confirm that there is minimal overlap between ARA and other SSc-specific autoantibodies. Additionally, it is demonstrated that the presence of ARA correlates with identifiable patterns by IIF on HEp-2 cell substrate.
authors.affiliation: Department of Clinical Immunology, Royal Free Hospital, London, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Parker
authors.forename: R W
authors.initials: RW
authors.lastname: Burlingame
authors.forename: T T
authors.initials: TT
authors.lastname: Webb
authors.forename: C C
authors.initials: CC
authors.lastname: Bunn
mesh_terms: D000974:Antibodies, Antinuclear / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods; D006801:Humans; D012320:RNA Polymerase III / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000276:immunology*; D012680:Sensitivity and Specificity
chemical_list: D000974:Antibodies, Antinuclear; D012320:RNA Polymerase III