HIV incidence assays are major epidemiological tools for fighting the HIV epidemic. These products represent a laboratory-based assay approach for conducting HIV-1 surveillance, enabling the estimation of HIV-1 incidence rates. Unlike “prevalence” which is a measure of the number of infected individuals per given number of persons (i.e. a population), “incidence” is the number of new infections per given number of persons (i.e. population) over a period of time. Classical diagnostic tests which indicate whether or not an individual is infected, can determine prevalence, but not incidence, since they do not determine if the infected individual was infected recently (i.e. a “new” infection) or was infected a long time ago (a “long term” infection). Incidence assays measure the recency of infection and can therefore be used to discriminate recent from long term infections. Such laboratory assays have significant advantages over the classical method of determining incidence which involves longitudinal cohort studies. In such studies, a statistically significant population of uninfected at-risk individuals is tracked over time and the number of HIV infections that develop in that population is counted and reported as the incidence rate (e.g. number of new infections per 100,000 persons per year). Use of longitudinal cohorts is significantly more complex, expensive, and time-consuming than HIV incidence assays, and have their own built-in biases depending on study design. Sedia manufactures HIV-1 incidence assays based on the Sedia®HIV-1 Limiting Antigen (LAg) Avidity EIA.

Incidence assays determine the proportion of HIV infections in a population that are recent versus long term infections. The Sedia® LAg-Avidity EIA determines the avidity or “binding strength” of the HIV-1 antibodies present in an infected individual’s blood.  Avidity is a measure of antibody maturation and progression of immune response, since the body “learns” to make more effective antibodies capable of binding “more tightly” to the virus as the immune response develops. Thus, early infections result in production of antibodies of lower avidity or weaker binding strength while later stage infections result in production of antibodies with higher avidity or stronger binding strength.

Knowing which infections in a population are recent and the ability to estimate incidence is of value to epidemiologists, public health officials, HIV intervention program managers and vaccine trial coordinators because it identifies the “hot spots” of infections. When those spots are determined, targeted populations are identified and decisions can be made about where to focus intervention efforts to maximize use of public health resources. This information is also useful to determine if HIV intervention efforts are working by monitoring whether the proportion of recent HIV infections is declining. The first generation of laboratory incidence tests offered the same approach, but were made by modifying commercial HIV diagnostic products to make them less sensitive, based on the principle of higher antibody levels in long term infections. Unfortunately, such an approach had a variable response to different HIV serotypes, since nearly all commercial diagnostic tests are made with only B serotype antigens, while the LAg-Avidity EIA was designed to react across all HIV serotypes. Sedia has quickly become the primary supplier of these assays, the fundamental technology of which was developed by the U.S. Centers for Disease Control and Prevention (CDC). In fact, all of Sedia’s HIV-1 Incidence Assays are tested and qualified by the CDC prior to product release. The assays are used as tools for monitoring the spread of HIV infections around the world, and are broadly preferred by experts in the area of HIV surveillance over other laboratory assay technologies.

Sedia’s scientific team has a long track record in working with the U.S. Centers for Disease Control and Prevention (CDC) and developing the first commercial assays for measuring recency of infection and estimating HIV-1 incidence, dating back over 10 years.  Our team has commercialized both the first HIV-1 BED Incidence EIA in 2004 and more recently the first HIV-1 LAg-Avidity EIA. Sedia maintains its leadership position by ensuring high quality HIV incidence assays for HIV programs around the world.

Sedia manufactures the following HIV Incidence Assays.

  1. Sedia® HIV-1 LAg-Avidity EIA

Additional information can be found by clicking on the product name above. Note that although these products are U.S. CDC tested and qualified, they are For Research Use Only, Not for Diagnostic Use.  They are typically used for surveillance studies, but are not intended for clinical management of individual patients.

Sedia’s HIV-1 LAg-Avidity EIA and Asanté HIV-1 Rapid Recency® Assay are both based on the same concept of using limiting antigen to distinguish recent or long term infections. However the Sedia® LAg-Avidity EIA is a lab-based test and needs a lab infrastructure, while the Rapid Recency® is a rapid lateral flow format and can be used at the Point-of-care level. The Rapid Recency® assay provides similar results to the LAg-Avidity EIA at a normalized ODn of 2.0 which correspond to a MDRI of 6 months.


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