title: [Function of flow cytometry on the dosage of antibodies against double stranded DNA in systemic lupus erythematosus].
abstract: BACKGROUND
  Among the diverse number of antibodies observed in systemic lupus erythematosus, antibodies against double stranded DNA (anti-dsDNA) represent important serologic markers for the disease diagnosis and the follow-up of the disease activity.
  
  
  OBJECTIVE
  To evaluate the role of a new quantitative methodology to detect antibodies against double stranded DNA in systemic lupus erythematosus and its association with the disease activity.
  
  
  METHODS
  The performance of the indirect immunofluorescence flow cytometry with Crithidia luciliae as substrate was compared with the Crithidia luciliae indirect immunofluorescence assay and the ELISA technique in order to detect antibodies against double stranded DNA in 54 sera from 47 patient with systemic lupus erythematosus and 100 sera from normal controls.
  
  
  RESULTS
  The new method showed a sensitivity of 78% and a specificity of 81% when the Crithidia luciliae indirect immunofluorescence assay was the gold standard. Compared with the ELISA technique, the flow cytometry showed a sensitivity of 78% and a specificity of 86%. No correlation was found among antibodies against double stranded DNA values detected with flow cytometry and the MEX-SLEDAI activity scores. However, the flow cytometry showed a sensitivity of 70% and a specificity of 42% to distinguish patients with systemic lupus erythematosus with and without activity (MEX-SLEDAI score > or = 5). The Rho intra-observer coefficient was 0.61 (p < 0.0001).
  
  
  CONCLUSIONS
  In spite of the fact that this new method might represent an interesting advance for antibodies against double stranded DNA quantitative testing, a clear superiority does not emerge when it was compared with more traditional assays. Difficulties related with its reproducibility might represent a limitation in the routine use of this new method.
authors.affiliation: Laboratorio de inmunología, Hospital Nacional de Clínicas. ferreropaola@hotmail.com
authors.forename: Paola V
authors.initials: PV
authors.lastname: Ferrero
authors.forename: Cristina
authors.initials: C
authors.lastname: Drenkard
authors.forename: César
authors.initials: C
authors.lastname: Collino
authors.forename: María José
authors.initials: MJ
authors.lastname: Cabral
authors.forename: Susana
authors.initials: S
authors.lastname: Gamron
authors.forename: Gloria
authors.initials: G
authors.lastname: Barberis
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Onetti
authors.forename: Emilia M
authors.initials: EM
authors.lastname: Menso de Ezcurra
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004247:DNA / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000175:diagnosis*; D008297:Male; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D004247:DNA