title: Detection of antinuclear antibodies by solid-phase immunoassays and immunofluorescence analysis.
abstract: BACKGROUND
  Antinuclear antibodies (ANAs) are associated with several inflammatory rheumatic diseases. The aim of the present work was to evaluate enzyme immunoassays (EIAs) and compare them with classic immunofluorescent analysis (IFA) for the detection of ANA.
  
  
  METHODS
  Seven enzyme immunoassays were used in this study. All assays were applied as described by the manufacturers. Three populations were included in the study: (a) a population of patients with well-established autoimmune inflammatory disease (n = 102); (b) a population in which a rheumatic disease was diagnosed up to 5 years after an IFA was performed (n = 164); and (c) a population of consecutive outpatients suspected to have a rheumatic disease (n = 101). The current clinical diagnoses of the patients served as the standard against which performance of the assays was evaluated.
  
  
  RESULTS
  In patients with well-established rheumatic disorders, the newly developed EIA in which HEp-2 extracts were included had sensitivities and specificities comparable to or in some instances better than the IFA. The assays without HEp-2 extracts included had significantly lower sensitivities and specificities. In the outpatient population, up to 51% of patients had positive ANA tests that did not correspond to classic ANA-associated disease. However, in the assays in which the HEp-2 extracts were not included, the false-positive rate was <10%. The false-negative rate judged against IFA differed from assay to assay and disease to disease and was mostly <10%.
  
  
  CONCLUSIONS
  In this study, the sensitivities of EIAs and IFA were largely comparable. However, EIAs without HEp-2 extracts included had a low sensitivity but a high specificity, particularly in nonselected populations. The choice of test is highly dependent on the clinical setting in which the ANA test is to be used and on laboratory policy.
authors.affiliation: Department of Clinical Biochemistry, University Hospital of Copenhagen, Hvidovre, Denmark. mogens.fenger@hh.hosp.dk
authors.forename: Mogens
authors.initials: M
authors.lastname: Fenger
authors.forename: Allan
authors.initials: A
authors.lastname: Wiik
authors.forename: Mimi
authors.initials: M
authors.lastname: Høier-Madsen
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Lykkegaard
authors.forename: Teresa
authors.initials: T
authors.lastname: Rozenfeld
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hansen
authors.forename: Bente Danneskjold
authors.initials: BD
authors.lastname: Samsoe
authors.forename: Søren
authors.initials: S
authors.lastname: Jacobsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000974:Antibodies, Antinuclear / Q000097:blood*; D001327:Autoimmune Diseases / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D008875:Middle Aged; D012216:Rheumatic Diseases / Q000175:diagnosis*
chemical_list: D000974:Antibodies, Antinuclear