Abstract
Laboratory assays for identifying recent HIV-1 infections are widely used for estimating incidence in cross-sectional population-level surveys in global HIV-1surveillance. Adequate assay and laboratory performance are required to ensure accurate incidence estimates. The NIAID-supported External Quality Assurance Program Oversight Laboratory (EQAPOL) established a proficiency testing program for the most widely-used incidence assay, the HIV-1 Limiting Antigen Avidity EIA (LAg), with US Centers for Disease Control and Prevention (CDC)-approved kits manufactured by Sedia Biosciences Corporation and Maxim Biomedical. The objective of this program is to monitor the performance of participating laboratories. Four rounds of blinded external proficiency (EP) panels were distributed to up to twenty testing sites (7 North American, 5 African, 4 Asian, 2 South American and 2 European). These panels consisted of ten plasma samples: three blinded well-characterized HIV-1-seropositive samples that were included as replicates and an HIV-negative control. The seropositive samples spanned the dynamic range of the assay and are categorized as either recent or long-term infection. Participating sites performed the assay according to manufacturers’ instructions and completed an online survey to gather information on kit manufacturer, lot of kit used, laboratory procedures and the experience of technicians. On average, fifteen sites participated in each round of testing, with an average of four sites testing with only the Maxim assay, seven testing with only the Sedia assay and five sites utilizing both assays. Overall, the Sedia and Maxim assays yielded similar infection status categorization across the laboratories; however, for most of the nine HIV+ samples tested, there were significant differences in the optical density readouts, ODn (N = 8) and OD (N = 7), between LAg kit manufacturers (p < 0.05 based on mixed effects models. The EQAPOL LAg program is important for monitoring laboratory performance as well as detecting variations between manufacturers of HIV-1incidence assays.
Highlights
Assays to identify recent HIV infection have revolutionized the science of incidence calculation and surveillance[1–3]
For each external proficiency panels (EPs), summary results were calculated from the reported classifications, calibrator Optical Density (OD) and test sample OD/optical densities (ODn)
External quality assurance for the Limiting Antigen Avidity EIA (LAg) assay participating sites were developed based on observed performance in EP1 and EP2 and implemented for EP3 and EP4, with EP2 being retrospectively graded
Summary
Assays to identify recent HIV infection have revolutionized the science of incidence calculation and surveillance[1–3]. While HIV incidence can be calculated from longitudinal HIV surveillance studies, they are expensive to support and prone to bias [2,5,6]. Cross-sectional incidence testing enables identification of recent infections in individuals who receive an HIV positive test result and is a more efficient way to calculate incidence in the surveillance population. Several additional incidence tests were developed and used in the US and at US-funded international sites, but it quickly became evident that assays were overestimating incidence calculations due to assay bias [10] in field studies [9], for reasons such as cohorts with treatment or natural control of HIV infection. Harmonization of techniques to measure recent HIV infection, and to calculate incidence in populations, is essential for producing reliable and consistent results[3]
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