title: Clinical performance of the Multispot HIV-1/HIV-2 rapid test to correctly differentiate HIV-2 from HIV-1 infection in screening algorithms using third and fourth generation assays and to identify cross reactivity with the HIV-1 Western Blot.
abstract: BACKGROUND
  An accurate and rapid serologic method to differentiate HIV-2 from HIV-1 infection is required since the confirmatory HIV-1 Western Blot (WB) may demonstrate cross-reactivity with HIV-2 antibodies.
  
  
  OBJECTIVE
  To evaluate the performance of the Bio-Rad Multispot HIV-1/HIV-2 rapid assay as a supplemental test to correctly identify HIV-2 infection and identify HIV-1 WB cross-reactivity with HIV-2 in clinical samples tested at an academic medical center.
  
  
  METHODS
  Between August 2008 and July 2012, clinical samples were screened for HIV using either 3rd- or 4th-generation HIV-1/2 antibody or combination antibody and HIV-1 p24 antigen assays, respectively. All repeatedly reactive samples were reflexed for Multispot rapid testing. Multispot HIV-2 and HIV-1 and HIV-2-reactive samples were further tested using an HIV-2 immunoblot assay and HIV-1 or HIV-2 RNA assays when possible. The HIV-1 WB was performed routinely for additional confirmation and to assess for HIV-2 antibody cross-reactivity.
  
  
  RESULTS
  Of 46,061 samples screened, 890 (89.6%) of 993 repeatedly reactive samples were also Multispot-reactive: 882 for HIV-1; three for only HIV-2; and five for both HIV-1 and HIV-2. All three HIV-2-only Multispot-positives along with a single dually reactive HIV-1/2 Multispot-positive were also HIV-2 immunoblot-positive; the latter was HIV-1 RNA negative and HIV-2 RNA positive.
  
  
  CONCLUSIONS
  The Multispot rapid test performed well as a supplemental test for HIV-1/2 diagnostic testing. Four new HIV-2 infections (0.45%) were identified from among 890 Multispot-reactive tests. The use of HIV-1 WB alone to confirm HIV-1/2 screening assays may underestimate the true prevalence of HIV-2 infection in the United States.
authors.affiliation: Department of Laboratory Medicine, Division of Virology, University of Washington, Seattle, USA. Electronic address: emramos@uw.edu.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Ramos
authors.affiliation: Department of Laboratory Medicine, Division of Virology, University of Washington, Seattle, USA.
authors.forename: Socorro
authors.initials: S
authors.lastname: Harb
authors.affiliation: Department of Laboratory Medicine, Division of Virology, University of Washington, Seattle, USA.
authors.forename: Joan
authors.initials: J
authors.lastname: Dragavon
authors.affiliation: Department of Laboratory Medicine, Division of Virology, University of Washington, Seattle, USA; Department of Medicine, Division of Allergy and Infectious Diseases, University of Washington, Seattle, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Coombs
mesh_terms: D000046:Academic Medical Centers; D000465:Algorithms; D015153:Blotting, Western / Q000379:methods; D019411:Clinical Laboratory Techniques / Q000379:methods*; D003955:Diagnostic Tests, Routine / Q000379:methods*; D015483:HIV Antibodies / Q000097:blood*; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology*; D015497:HIV-1 / Q000145:classification* / Q000276:immunology; D015498:HIV-2 / Q000145:classification* / Q000276:immunology; D006801:Humans; D015151:Immunoblotting; D025202:Molecular Diagnostic Techniques; D012189:Retrospective Studies; D012698:Serologic Tests / Q000379:methods; D014481:United States; D014773:Virology / Q000379:methods
chemical_list: D015483:HIV Antibodies
keywords: HIV testing algorithms; HIV-2; Multispot; Nucleic acid amplification tests; Orthogonal supplemental testing