Evaluation of two antibodies against double-stranded DNA assays in discriminating between active and non-active systemic lupus erythematosus: correlation between the cut-off and the specificity

Pathol Biol (Paris). 2012 Dec;60(6):387-91. doi: 10.1016/j.patbio.2011.12.003. Epub 2012 Jan 20.


This study aimed to evaluate, improve and compare the performances of two anti-double-stranded DNA (dsDNA) detection kits, differing by their affinity, in discriminating between active and non-active systemic lupus erythematosus (SLE). Eighty-two anti-nuclear antibody positive sera (45 patients) were tested by two anti-dsDNA commercial quantitative assays (Fidis™, Farrzyme™). All the patients fulfilled at least four of the revised American College of Rheumatology criteria. SLE disease activity was assessed using a modified SLEDAI to remove anti-dsDNA descriptors. When using the manufacturers' cut-offs, no difference in the frequency of positive results was found with respect to disease activity, with Fidis™. On the contrary, with Farrzyme™, a significantly higher frequency of positive sera was found in active SLE patients. Nonetheless, poor performances were observed for both tests. With thresholds defined by ROC methodology, 212IU/mL for Fidis™ (Se: 83.9%, Sp: 86.3%), and 68.8IU/mL for Farrzyme (Se: 71.0%, Sp: 96.1%), a great improvement of the accuracy of the two methods was observed. Moreover, the better specificity and pLR, obtained after optimization of the Farrzyme™ test, could also be obtained with the Fidis™ assay by using a higher threshold than that obtained after optimization of the test. We concluded that when using manufacturers' cut-offs, the two assays appeared to be of poor clinical usefulness in the determination of disease activity. A great improvement was observed using higher thresholds. Moreover, a good concordance could be observed between the two assays (κ=0.764).

Publication types

  • Evaluation Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antibodies* / immunology
  • Antibodies, Antinuclear / blood
  • Antibody Affinity
  • Child
  • DNA / blood*
  • DNA / immunology*
  • Female
  • Humans
  • Immunoassay / methods*
  • Immunoglobulin G / immunology
  • Lupus Erythematosus, Systemic / blood*
  • Male
  • Middle Aged
  • Reagent Kits, Diagnostic
  • Sensitivity and Specificity


  • Antibodies
  • Antibodies, Antinuclear
  • Immunoglobulin G
  • Reagent Kits, Diagnostic
  • DNA