title: Analytical evaluation of nine serological assays for diagnosis of syphilis.
abstract: BACKGROUND
  The diagnosis of syphilis is most frequently dependent on antibody detection with serological assays. Assays for both treponemal and non-treponemal antibodies are needed to provide a sensitive and specific diagnosis. For decades, a first screening has been done with non-treponemal assays, followed by treponemal. However, in recent years, following laboratory automation, the reverse sequence screening algorithms have been developed, using a treponemal assay as the initial screening test.
  
  
  OBJECTIVE
  To evaluate serological assays for treponemal and non-treponemal antibodies, to use in reverse algorithm screening of syphilis.
  
  
  METHODS
  Six treponemal assays (one IgM-specific assay), two non-treponemal assays and one novel dual point-of-care (POC) assay for serological diagnosis of syphilis were evaluated. Serum samples from Guinea-Bissau and Sweden were examined, as well as two performance panels and samples from blood donors. Sensitivity and specificity were calculated for each assay, using different assays as gold standard test.
  
  
  RESULTS
  The Macro-Vue RPR Card test was the most sensitive non-treponemal test and the TrepSure Anti-Treponema EIA Screen and the SeroDia TP-PA were the most sensitive and specific treponemal assays. Among the automated assays, both the Liaison Treponema Screen and Architect Syphilis TP showed high sensitivity, however, the former had clearly higher specificity.
  
  
  CONCLUSIONS
  In resourced settings, where the reverse sequence algorithm is preferred for screening, an automated treponemal immunoassay for initial screening subsequently followed by the TrepSure test or TP-PA assay as a second treponemal assay appear highly effective. Finally, a quantitative highly sensitive non-treponemal assay, e.g. the Macro-Vue RPR Card test, could then be used as a supplementary test to evaluate activity of the syphilis infection.
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Malm
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Andersson
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Fredlund
authors.affiliation: Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Norrgren
authors.affiliation: National Public Health Laboratory (LNSP), Bissau, Guinea-Bissau.
authors.forename: A
authors.initials: A
authors.lastname: Biague
authors.affiliation: Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Månsson
authors.affiliation: Center for Global Health, Centers for Disease Control and Protection, Atlanta GA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Ballard
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Unemo
mesh_terms: D000465:Algorithms; D000907:Antibodies, Bacterial / Q000097:blood*; D002308:Cardiolipins / Q000276:immunology; D005428:Flocculation Tests; D006169:Guinea-Bissau; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D019095:Point-of-Care Systems; D012680:Sensitivity and Specificity; D013548:Sweden; D013587:Syphilis / Q000175:diagnosis*; D013588:Syphilis Serodiagnosis / Q000379:methods*; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D002308:Cardiolipins; D007075:Immunoglobulin M
keywords: Syphilis; Treponema pallidum; immunoassays; non-treponemal antibodies; screening algorithms; treponemal antibodies