title: Significant differences in the analytic concordance between anti-dsDNA IgG antibody assays for the diagnosis of systemic lupus erythematosus--implications for inter-laboratory testing.
abstract: BACKGROUND
  Anti-double stranded DNA (anti-dsDNA) autoantibodies are considered hallmark of systemic lupus erythematosus (SLE).
  
  
  METHODS
  To determine concordance between assays for the detection of this marker, we analyzed 100 antinuclear antibody (ANA) positive sera with a homogeneous pattern and titers≥1:160 by indirect immunofluorescence assay (IFA) on HEp-2 cells, 100 consecutive anti-dsDNA IgG ELISA-negative as well as 100 healthy control samples using six commercial ELISAs and the Crithidia luciliae immunofluorescence test (CLIFT).
  
  
  RESULTS
  The positivity rates for the ELISAs in the ANA positive group ranged from 55.0 to 88.0% with specificities from 84.0 to 98.0%. The CLIFT had a positivity rate of 68.0% and specificity of 84%. In the previously screened anti-dsDNA IgG-negative group, the positivity rates ranged from 1 to 19%. The overall correlations between the ELISAs ranged from 73.0 to 89.5% and varied from 70.0 to 80.0% among specific ELISAs and CLIFT.
  
  
  CONCLUSIONS
  Our data show variable degree of concordance between anti-dsDNA IgG ELISAs which may significantly impact inter-laboratory testing as well as the diagnosis and management of SLE patients. Although some of the ELISAs show comparable performance to the CLIFT, the degree of concordance between these assays at high antibody levels suggests that CLIFT is still a relevant confirmatory tool.
authors.affiliation: Associated Regional and University Pathologists (ARUP) Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108-1221, United States.
authors.forename: Tyson R
authors.initials: TR
authors.lastname: Chiaro
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Davis
authors.forename: Andrew
authors.initials: A
authors.lastname: Wilson
authors.forename: Brenda
authors.initials: B
authors.lastname: Suh-Lailam
authors.forename: Anne E
authors.initials: AE
authors.lastname: Tebo
mesh_terms: D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods*; D003421:Crithidia / Q000166:cytology; D004247:DNA / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology*; D007753:Laboratories; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
chemical_list: D007074:Immunoglobulin G; D004247:DNA