title: Specific chemoluminescence and immunoasdorption tests for anti-DFS70 antibodies avoid false positive results by indirect immunofluorescence.
abstract: OBJECTIVE
  To evaluate two new diagnostic methods for the identification of anti-DFS70 antibodies in samples showing a DFS70-staining pattern by indirect immunofluorescence (IIF).
  
  
  METHODS
  We studied 731 patients: 576 were collected consecutively among those that in the ANA test on HEp-2 cells had produced a DFS70 fluorescence pattern and 155 were a consecutive series of patients sent by referring physicians for routine ANA testing. As controls we studied 50 patients with autoimmune diseases and 120 patients with active infectious disease. All 731 sera were assayed for anti-DFS70 antibodies by a specific chemoluminescence assay (CLIA); 70 randomly selected IIF-positive sera and 35 samples from patients with autoimmune diseases were studied by inhibition tests using the HEp-2 Select method.
  
  
  RESULTS
  Assays performed with the CLIA-DFS70 method were positive in 30.4% of the samples presenting a DFS70 pattern by IIF, in 1.3% of the routine ANA sera, in 1.6% of the infectious sera and in none of the 50 autoimmune controls. However, as the IIF-DFS70 positive group included 106 patients with systemic autoimmune rheumatic diseases (SARD), 11 of which were DFS70 positive by CLIA, the prevalence of DFS70 antibodies in SARD was 7.5%. The ANA test performed after the use of HEp-2 Select showed an inhibition in 95.7% of the sera. No change in fluorescence intensity and pattern morphology between the native sera and the same sera tested with the solution containing the DFS70 antigen was observed in the 35 samples from patients with autoimmune diseases.
  
  
  CONCLUSIONS
  To avoid misinterpretation of ANA pattern and consequent diagnostic errors, confirmation of the DFS70-IIF pattern by CLIA or other specific methods is mandatory before reporting the presence of anti-DFS70 antibodies. The HEp-2 Select test in most cases eliminates the interference by anti-DFS70 antibodies and avoids the possible reporting of false positive results.
authors.affiliation: Laboratorio di Patologia Clinica, Ospedale San Antonio, Tolmezzo, Italy. Electronic address: nicola.bizzaro@aas3.sanita.fvg.it.
authors.forename: Nicola
authors.initials: N
authors.lastname: Bizzaro
authors.affiliation: Immunopatologia e Allergologia, Azienda Ospedaliero-Universitaria S. Maria della Misericordia, Udine, Italy.
authors.forename: Elio
authors.initials: E
authors.lastname: Tonutti
authors.affiliation: Laboratorio di Patologia Clinica, Policlinico Universitario, Bari, Italy.
authors.forename: Marilina
authors.initials: M
authors.lastname: Tampoia
authors.affiliation: Laboratorio di Immunologia e Allergologia, Ospedale S. Giovanni di Dio, Firenze, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Infantino
authors.affiliation: Laboratorio di Patologia Clinica, Ospedale San Antonio, Tolmezzo, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cucchiaro
authors.affiliation: Laboratorio di Patologia Clinica, Ospedale San Antonio, Tolmezzo, Italy.
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Pesente
authors.affiliation: Dipartimento di Medicina Clinica e Scienze Immunologiche, Sezione di Reumatologia, Policlinico Universitario Le Scotte, Siena, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Morozzi
authors.affiliation: Istituto di Patologia Clinica, Azienda Ospedaliero-Universitaria S. Maria della Misericordia, Udine, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Fabris
authors.affiliation: Allergologia e Immunologia Clinica, Azienda Ospedaliera S. Maria degli Angeli, Pordenone, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Villalta
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood* / Q000276:immunology*; D045744:Cell Line, Tumor; D002648:Child; D002675:Child, Preschool; D005189:False Positive Reactions; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007163:Immunosorbent Techniques; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D014157:Transcription Factors / Q000276:immunology*; D055815:Young Adult
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; C504649:PSIP1 protein, human; D014157:Transcription Factors
keywords: Antinuclear antibodies; Autoimmune rheumatic diseases; Chemoluminescence; DFS70; Immunoadsorption; LEDGF/75