Less sensitive (LS) HIV-1 enzyme immunoassays (EIAs) have significantly improved the quantity and quality of HIV surveillance data. The first LS-HIV-1 EIA, the Abbott 3A11-LS, provided reliable incidence data, but the assay required specialized equipment, and the lack of available reagents made testing difficult. This study evaluated the use of an alternate assay, a modified version of the Vironostika HIV-1 EIA (Vironostika-LS), to be used for LS testing. The Vironostika-LS has similar performance characteristics to the Abbott 3A11-LS with additional advantages. This 96-well formatted assay is commonly found in public health laboratories for routine HIV-1 testing and can be used with both serum and dried blood spot specimens. The estimated mean time from seroconversion (defined using a standardized optical density cutoff of 1.0) with the Vironostika-LS was 170 days (95% CI, 145-200 days). When the Vironostika-LS was applied to a matched serum set previously tested with the Abbott 3A11-LS, the Vironostika-LS accurately identified 97% of specimens with recent or long-standing HIV infection. The paper also reports Vironostika-LS quality control guidelines and the results from 3 rounds of proficiency testing.
The Centers for Disease Control and Prevention (CDC) has proposed new strategies for HIV prevention. 1,2 An important component of these programs is the increased identification of people who are HIV positive. For the programs to be effective, enhanced prevention programs are needed to target populations with high incidences of HIV. 3 New laboratory technologies, epidemiologic methods, and public health prevention programs have significantly improved HIV surveillance. 4 The Serologic Testing Algorithm for Recent HIV Seroconversion (STARHS) is a 2-step testing algorithm that has played a significant role in accurately measuring HIV incidence. 5 In this algorithm, blinded patient samples are first tested with a sensitive enzyme immunoassay (EIA), and EIA-positive specimens are confirmed by conventional Western blot analysis. 6 Selected specimen sets are subsequently tested with a less sensitive (LS) EIA that determines whether the specimens represent a person with a longstanding or a recent HIV infection. This strategy has been used successfully to measure HIV incidence in several subpopulations including persons attending anonymous counseling and testing sites, patients in sexually transmitted disease clinics, and young men who have sex with men (YMS). 7-10
The first LS-HIV-1 EIA, the Abbott 3A11-LS (Abbott Laboratories, Abbott Park, IL), became available in the spring of 1998 to laboratories participating in CDC's Investigational New Device (IND) Application (held by the Food and Drug Administration [FDA]). We optimized the method, prepared a standardized laboratory protocol, and developed a quality assurance program to assist national and international public health laboratories with LS testing methodology and applications. These efforts were designed to ensure the comparability of data collected from different sources and settings. In January 2000, the FDA issued an injunction against Abbott Laboratories that resulted in a limitation on the number of Abbott 3A11 kits available to individual laboratories. Subsequently, alternate sensitive EIAs were evaluated as potential candidates for modification. After extensive analysis, the Abbott 3A11-LS (considered the original gold standard for LS EIA testing) was replaced with the Vironostika-LS, a modification of bioMérieux's Vironostika HIV-1 EIA (bioMérieux, Inc., Durham, NC). 11 The format of the Vironostika-LS assay had many advantages. The modified assay was based on the widely accepted 96-well plate format, and the extra diluent needed for specimen dilutions was readily available. Additionally, many state and local public health laboratories use the 96-well plate format for routine HIV-1 screening and are familiar with the general assay procedure.
We describe here our quality assurance measures developed for the 3A11-LS protocol. Although the 3A11 assay in no longer available, the quality assurance measures developed for it formed the basis for the quality assurance protocol developed for the Vironostika-LS. We describe the statistical validation of the Vironostika-LS assay and the definition of the window period (time between seroconversion on a sensitive assay and the Vironostika-LS). We also report results from stability studies on quality control (QC) materials and describe the suggested QC guidelines for the Vironostika-LS as well as results from 3 rounds of proficiency testing.