title: Use of "biokit HSV-2 Rapid Assay" to improve the positive predictive value of Focus HerpeSelect HSV-2 ELISA.
abstract: BACKGROUND
  Commercially available assays to detect antibodies to the herpes simplex virus type 2 (HSV-2)-specific glycoprotein gG-2 have markedly improved serologic diagnosis of HSV-2 infection. However, even tests with high specificity can have low positive predictive values in low prevalence populations. HSV-2 is a chronic, life-long viral infection that requires both medical attention and potential alterations in health care strategy. As such, the concern for false positive diagnoses is high confirmatory testing is routine for other viral serologies such as HIV and hepatitis C. We evaluated such a strategy for HSV-2 serology by using an easily performed commercial test, biokitHSV-2 rapid test ("Biokit"; Biokit USA, Lexington MA) as a confirmatory test for the widely used gG-2 specific serology ("Focus;" HerpeSelect HSV-2 ELISA; Focus Diagnostics, Cypress CA).
  
  
  METHODS
  We tested 782 sera by Focus HSV-2 ELISA, Biokit, and the current gold standard test, Western blot (WB).
  
  
  RESULTS
  The positive predictive value of the Focus HSV-2 ELISA increased from 80.5% to 95.6% when Biokit testing was performed on sera that were initially positive by Focus HSV-2 ELISA. Confirmatory testing increased the specificity markedly among sera with Focus EIA values between 1.1 and 3.5: only 35% of low positive (index values 1.1-3.5) Focus HSV-2 ELISA results confirmed as positive by Biokit and WB compared with 92% of those with index values >3.5. Mathematical modeling of the data resulted in expected positive predictive values over 98% for populations with antibody prevalences typical of clinical practices in the US and Europe.
  
  
  CONCLUSIONS
  Confirmatory Biokit testing of positive Focus HSV-2 ELISA results is fast, easy, and effective in reducing falsely positive HSV-2 antibody results. Patients, clinicians, and laboratories could benefit from the enhanced specificity of this simple HSV-2 serologic test combination.
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA. rhoda.morrow@seattlechildrens.org
authors.forename: Rhoda Ashley
authors.initials: RA
authors.lastname: Morrow
authors.forename: David
authors.initials: D
authors.lastname: Friedrich
authors.forename: Amalia
authors.initials: A
authors.lastname: Meier
authors.forename: Lawrence
authors.initials: L
authors.lastname: Corey
mesh_terms: D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D006558:Herpes Genitalis / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D018258:Herpesvirus 2, Human / Q000276:immunology* / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D011933:Reagent Kits, Diagnostic