title: Detection of anti-nuclear antibodies by indirect immunofluorescence on HEp-2 cells: setting the appropriate screening dilution for the diagnosis of autoimmune rheumatic diseases.
abstract: OBJECTIVE
  To establish the abnormal title and the appropriate screening dilution for ANA (antinuclear antibodies) test by indirect immunofluorescence on HEp-2 cells (ANA HEp-2).
  
  
  METHODS
  An analysis of ANA Hep-2 in serum samples from 126 healthy individuals was performed. The samples were screened at a dilution of 1:80, and those positive were diluted to the title of 1:5120. The abnormal title of ANA was defined as that corresponding to the 95th percentile of the test in this population. The sensitivity of the different titles of antinuclear antibodies was determined in a group of 136 patients with a diagnosis of autoimmune rheumatic disease, and the specificity was determined in a group of 118 patients with other rheumatic diseases. The optimal cutoff value of the test was determined by ROC curve analysis.
  
  
  RESULTS
  The frequency of ANA positivity in healthy subjects was 13.2%. There was no difference in the frequency of positive results according to gender or age. The abnormal title of ANA was defined as the dilution of 1:160. The 1:80 dilution had sensitivity of 87.7% and specificity of 67.8%, while the 1:160 dilution had sensitivity of 82% and specificity of 73.7%. By ROC curve analysis, a dilution of 1:160 corresponded to the optimal cutoff value.
  
  
  CONCLUSIONS
  The abnormal title and the optimal cutoff value of ANA HEp-2 in the population was 1:160. Therefore, the dilution of 1:160 is the optimal screening dilution, with better specificity but without significantly compromising the sensitivity of the diagnostic test.
authors.affiliation: Instituto Hermes Pardini, Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Fabiano de Almeida
authors.initials: Fde A
authors.lastname: Brito
authors.affiliation: Departamento de Propedêutica Complementar, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: Silvana Maria Elói
authors.initials: SM
authors.lastname: Santos
authors.affiliation: Departamento do Aparelho Locomotor, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: Gilda Aparecida
authors.initials: GA
authors.lastname: Ferreira
authors.affiliation: Instituto Hermes Pardini, Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: William
authors.initials: W
authors.lastname: Pedrosa
authors.affiliation: Instituto Hermes Pardini, Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Janaina
authors.initials: J
authors.lastname: Gradisse
authors.affiliation: Instituto Hermes Pardini, Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Lara Cristina
authors.initials: LC
authors.lastname: Costa
authors.affiliation: Departamento de Propedêutica Complementar, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: Suzane Pretti Figueiredo
authors.initials: SP
authors.lastname: Neves
mesh_terms: D000328:Adult; D000974:Antibodies, Antinuclear / Q000097:blood* / Q000302:isolation & purification*; D001327:Autoimmune Diseases / Q000097:blood* / Q000175:diagnosis* / Q000276:immunology; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000145:classification / Q000276:immunology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012216:Rheumatic Diseases / Q000097:blood* / Q000175:diagnosis* / Q000276:immunology
chemical_list: D000974:Antibodies, Antinuclear