title: Abnormal antinuclear antibody titers are less common than generally assumed in established cases of systemic lupus erythematosus.
abstract: OBJECTIVE
  To evaluate antinuclear antibody (ANA) tests in established cases of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) by indirect immunofluorescence microscopy (F-ANA) and enzyme-immunoassays detecting antinucleosomal antibodies (ANSA-EIA).
  
  
  METHODS
  Sera from 50 patients with SLE and 65 patients with RA were analyzed regarding abnormal concentrations of F-ANA (serum dilution>or=1:200=95th percentile among 300 healthy blood donors). The sera were also analyzed with 2 commercial ANSA-EIA kits.
  
  
  RESULTS
  An abnormal F-ANA titer occurred in 76% of the SLE sera compared to 23% in RA, and was not related to present use of antirheumatic drugs. At dilution 1:50, 84% of the SLE sera were F-ANA-positive compared to 20% of healthy women. Forty percent and 56%, respectively, of the SLE sera tested positive in the 2 ANSA-EIA kits. By the most sensitive assay, 96% of the ANSA-positive SLE sera produced a homogenous (chromosomal) F-ANA staining pattern compared to 18% of the ANSA-negative SLE sera. Ten of the 15 F-ANA-positive RA sera (63%) generated homogenous F-ANA staining and 13 (20%) tested positive in the most sensitive ANSA-EIA, but with no correlation to the F-ANA staining pattern.
  
  
  CONCLUSIONS
  The sensitivity of F-ANA at an abnormal titer was surprisingly low (76%) in established cases of SLE. ANSA occurred in 56% of the SLE sera, but also in a fair number (20%) of RA sera. Practically all ANSA-positive SLE sera were identified by chromosomal F-ANA staining. We conclude that the antigen-specific antinucleosomal EIA does not have high enough diagnostic specificity to justify use of this analysis for routine diagnostic purposes.
authors.affiliation: Division of Rheumatology, Autoimmunity and Immune Regulation unit (AIR) and Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping University Hospital, Linköping, Sweden.
authors.forename: Christopher
authors.initials: C
authors.lastname: Sjöwall
authors.forename: Martin
authors.initials: M
authors.lastname: Sturm
authors.forename: Charlotte
authors.initials: C
authors.lastname: Dahle
authors.forename: Anders A
authors.initials: AA
authors.lastname: Bengtsson
authors.forename: Andreas
authors.initials: A
authors.lastname: Jönsen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Sturfelt
authors.forename: Thomas
authors.initials: T
authors.lastname: Skogh
mesh_terms: D000328:Adult; D000974:Antibodies, Antinuclear / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000974:Antibodies, Antinuclear; D015415:Biomarkers