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.

Conclusion: 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.

Figure 1. Performance of in-house assay versus prototype kit.

The normalized MFI values (n) and avidity index (a) for the in-house assay and kit were compared for drug naïve, known recent (infected <6 months) and long-term (infected >1 year) specimens. The boxes represent the 25^th to 75^th percentile of reactivity, while the middle lines represent the median values. Black dots indicate the 5^th to 95^th percentile of reactivity.

Figure 2. Inter-laboratory reproducibility of kit measures.

The normalized MFI values and avidity index of longitudinal seroconversion panels were compared for the three participating laboratories. The values for each laboratory were plotted on a separate axis.

Figure 3. Inter-laboratory kit performance.

The normalized MFI values (n) and avidity index (a) of known recent and long-term specimens, as measured by the prototype kits, were compared for each laboratory.