title: 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.
abstract: 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).
authors.affiliation: Laboratoire d'immunologie, CHU de Nantes, 5 allée de l'Île-Gloriette, Nantes, France. jer.martin@yahoo.fr
authors.forename: J
authors.initials: J
authors.lastname: Martin
authors.forename: C
authors.initials: C
authors.lastname: Durant
authors.forename: M
authors.initials: M
authors.lastname: Rimbert
authors.forename: C
authors.initials: C
authors.lastname: Hemont
authors.forename: M
authors.initials: M
authors.lastname: Hamidou
authors.forename: M
authors.initials: M
authors.lastname: Audrain
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000906:Antibodies / Q000276:immunology; D000974:Antibodies, Antinuclear / Q000097:blood; D000915:Antibody Affinity; D002648:Child; D004247:DNA / Q000097:blood* / Q000276:immunology*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies; D000974:Antibodies, Antinuclear; D007074:Immunoglobulin G; D011933:Reagent Kits, Diagnostic; D004247:DNA