title: Inter-laboratory assessment of a prototype multiplex kit for determination of recent HIV-1 infection.
abstract: BACKGROUND
  Accurate and reliable laboratory-based assays are needed for estimating HIV-1 incidence from cross-sectional samples. We recently described the development of a customized, HIV-1-specific Bio-Plex assay that allows for the measurement of HIV-specific antibody levels and avidity to multiple analytes for improved HIV-1 incidence estimates.
  
  
  METHODS
  To assess intra- and inter-laboratory assay performance, prototype multiplex kits were developed and evaluated by three distinct laboratories. Longitudinal seroconversion specimens were tested in parallel by each laboratory and kit performance was compared to that of an in-house assay. Additionally, the ability of the kit to distinguish recent from long-term HIV-1 infection, as compared to the in-house assay, was determined by comparing the reactivity of known recent (infected <6 months) and long-term (infected >12 months) drug naïve specimens.
  
  
  RESULTS
  Although the range of reactivity for each analyte varied between the prototype kit and in-house assay, a measurable distinction in reactivity between recent and long-term specimens was observed with both assays in all three laboratories. Additionally, kit performance was consistent between all three laboratories. The intra-assay coefficient of variation (CV), between sample replicates for all laboratories, ranged from 0.5% to 6.1%. The inter-laboratory CVs ranged from 8.5% to 21.3% for gp160-avidity index (a) and gp120-normalized mean fluorescent intensity (MFI) value (n), respectively.
  
  
  CONCLUSIONS
  We demonstrate the feasibility of producing a multiplex kit for measuring HIV antibody levels and avidity, with the potential for improved incidence estimates based on multi-analyte algorithms. The availability of a commercial kit will facilitate the transfer of technology among diverse laboratories for widespread assay use.
authors.affiliation: Laboratory Branch, Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Curtis
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Longosz
authors.forename: M Susan
authors.initials: MS
authors.lastname: Kennedy
authors.forename: Sheila
authors.initials: S
authors.lastname: Keating
authors.forename: John
authors.initials: J
authors.lastname: Heitman
authors.forename: Oliver
authors.initials: O
authors.lastname: Laeyendecker
authors.forename: S Michele
authors.initials: SM
authors.lastname: Owen
mesh_terms: D000465:Algorithms; D003430:Cross-Sectional Studies; D015483:HIV Antibodies / Q000276:immunology; D015658:HIV Infections / Q000276:immunology*; D006801:Humans
chemical_list: D015483:HIV Antibodies