title: Performance of an alternative HIV diagnostic algorithm using the ARCHITECT HIV Ag/Ab Combo assay and potential utility of sample-to-cutoff ratio to discriminate primary from established infection.
abstract: BACKGROUND
  The ARCHITECT HIV Ag/Ab Combo assay has a wide dynamic range for determining the sample-to-cutoff ratio (S/CO) values compared to other diagnostic HIV antibody assays.
  
  
  OBJECTIVE
  Determine the performance of an HIV testing algorithm that uses the ARCHITECT combo assay in the clinical setting and explore the utility of the signal-to-cutoff (S/CO) ratio to predict acute HIV-1 infection status.
  
  
  METHODS
  A retrospective analysis of clinical samples from a hospital and referral population screened for HIV-1 infection between May 2011 and March 2013. Repeatedly reactive samples were tested using the Multispot HIV-1/HIV-2 rapid test and depending on that result, confirmatory orthogonal testing used the Western blot (WB) for HIV-1, Immunoblot for HIV-2 and nucleic acid amplification testing (NAAT) for HIV RNA.
  
  
  RESULTS
  A total of 21,317 test results were evaluated of which 509 were ARCHITECT repeatedly reactive; of these, 422 were Multispot-reactive only for HIV-1 (413 WB-positive; 9 indeterminate), 4 were Multispot-reactive for both HIV-1 and HIV-2 (one HIV-2 immunoblot-positive with 17 HIV-2 RNA copies/mL) and 83 were Multispot-non-reactive of which 15 were HIV-1 RNA positive and represented acute HIV-1 infection. There was an association among the ARCHITECT S/CO (median; IQR) values for antibody-negative (0.14; 0.11-0.16), acute infection (33; 2.1-76) and established HIV-1 infection (794; 494-1,029) (Kruskal-Wallis, p<0.0001).
  
  
  CONCLUSIONS
  The ARCHITECT combo assay with Multispot confirmation and reserved use of HIV-1 WB, HIV-2 Immunoblot and HIV NAAT for Multispot dual HIV-1/2 infection, and NAAT alone for Multispot-negative specimens, had a suitable test performance for detecting acute and established HIV infection.
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, United States. Electronic address: emramos@uw.edu.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Ramos
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, United States.
authors.forename: Socorro
authors.initials: S
authors.lastname: Harb
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, United States.
authors.forename: Joan
authors.initials: J
authors.lastname: Dragavon
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, United States; Public Health - Seattle and King County, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Swenson
authors.affiliation: Public Health - Seattle and King County, United States; Department of Medicine, University of Washington, Seattle, WA, United States.
authors.forename: Joanne D
authors.initials: JD
authors.lastname: Stekler
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, WA, United States; Department of Medicine, University of Washington, Seattle, WA, United States.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Coombs
mesh_terms: D000465:Algorithms; D003955:Diagnostic Tests, Routine / Q000379:methods*; D015483:HIV Antibodies / Q000097:blood*; D015488:HIV Antigens / Q000097:blood*; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology; D015497:HIV-1 / Q000145:classification* / Q000235:genetics / Q000276:immunology; D015498:HIV-2 / Q000145:classification* / Q000235:genetics / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000379:methods; D021141:Nucleic Acid Amplification Techniques / Q000379:methods; D012367:RNA, Viral / Q000097:blood*; D012189:Retrospective Studies; D014773:Virology / Q000379:methods
chemical_list: D015483:HIV Antibodies; D015488:HIV Antigens; D012367:RNA, Viral
keywords: ARCHITECT HIV Ag/Ab Combo assay; Alternative HIV diagnostic algorithm; Sample-to-cutoff ratio
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