CROI 2016 Abstract eBook

Abstract Listing

Poster Abstracts

513 Weakly Reactive HIV Rapid Diagnostic Test Kits Should Not Be Reported As Positive Patrick Karugaba 1 ;Timothy Amukele 2 ; Ali Elbireer 1 ; Alice Nansamba 1 1 Makerere Univ Johns Hopkins Univ Rsr Collab Lab, Kampala, Uganda; 2 Johns Hopkins Univ Sch of Med, Baltimore, MD, USA

Background: HIV rapid diagnostic test (RDT) kit manufacturers require that reactive bands observed in the test area of the kit are reported as positive regardless of intensity of coloration. Some studies have suggested that weakly reactive RDT results should not be considered positive except in blood donor screening. However, a reliable estimate of the proportion of weakly reactive bands in 3 rd generation HIV RDT’s that would actually be false positive has not been published. We assessed the percentage of weakly reactive bands that were subsequently confirmed negative by HIV DNA-PCR. Methods: Over an 11 year period (2002 to 2013) we determined the proportion of inconclusive results that were later confirmed negative by DNA PCR. Inconclusive results were based on the observance of a weakly reactive band on at least one of three 3 rd generation HIV RDT kits used within a sequential testing algorithm. The three kits were Alere Determine, Chembio Stat-Pak, and Uni-Gold. The algorithmwas as follows; all tests were initially run on Determine. If negative, reported as negative; if positive they were confirmed with Stat Pak. If discrepant, Uni-Gold was used as a tie breaker. HIV-1 DNA PCR Roche Amplicor Version 1.5 was used as the confirmatory test method. Results: 39,294(12.9%) of 303,010 individuals screened for HIV were positive. 468 (0.15%) of the same initially had inconclusive HIV RDT results. The HIV status of the 468 individuals was resolved by HIV-1 Western Blot (17), HIV-RNA PCR (14), or HIV-DNA PCR (437) confirmatory tests. 224 of the 437 cases confirmed by DNA-PCR RDT’s were independently repeated by another tech to control for individual variability. Only these 224 cases were included in this analysis. Of these 224 cases, 148 (66.1%) were negative by HIV DNA PCR. Of note, repeating the 224 tests gave a total of 448 instances of testing with both Determine and Sat-Pak RDT kits, and 441 testing instances with Uni-Gold kit. (Detailed results Table attached). Conclusions: The majority of weakly reactive RDT results from all three kits used turned out to be negative on confirmatory HIV DNA PCR testing. This is contrary to manufacturers’ instructions to interpret all such tests as positive. Our results also lend credence to previously published calls for testing algorithms to refer weakly reactive RDT test results for confirmatory testing. This is especially pertinent in the era of ART initiation based solely on HIV RDT results and scaled-up HIV surveillance programs in resource limited settings.

514

Extending HIV Avidity Recency Detection by Addition of p24Ag Detection Gary Murphy 1 ; Anne Le Corfec 2 ; Jamie Benson 3 ; Jake Hall 1 ; AlfredoVillarreal 4 ; Karen Mintern 3 1 PH England, London, UK; 2 Bio-Rad Lab, Inc, La Coquette, France; 3 Bio-Rad Lab, Inc, Hemel Hempstead, UK; 4 Bio-Rad Lab, Inc, Benicia, CA, USA

Background: Increasing the period in which HIV recency assays can identify recent infection without increasing misclassification of specimens as recent will allow studies to use smaller sample sizes. We describe an HIV avidity assay that identifies recent HIV infection by detection of low avidity antibodies along with detection of HIV p24 Ag in anti-HIV negative specimens thus extending the duration that recent HIV infection can be determined. Methods: Specimens were tested for using the BioPlex 2200 HIV Ag-Ab assay. This ‘5 th generation’ assay allows separate detection and identification of anti-HIV 1, anti-HIV-2 and HIV p24 Ag unlike 4 th generation which give a single signal. An antibody avidity modification using 1M guanidine allowed determination of an avidity index. Presence of p24 Ag was determined on each sample and a subset of specimens diluted with Guanidine and PBS. Results were compared with an existing HIV incidence assay (HIV Limiting Antigen). 150 specimens were tested comprising HIV seroconversion panels, known anti-HIV positive specimens and acute p24 Ag only positive specimens were used. Results: Antibody avidity increased over time. Where p24 Ag was detected prior to seroconversion addition of guanidine and/or dilution of specimen had only a minimal effect on level of p24 detection but it remained detectable. Using a cut-off of <80% AI for recent infection concordance with LAg assay result was over 90%. Of four mismatched specimens two were close to the recency cut-off for either LAg or BioPlex avidity. Conclusions: This assay has a sensitive and specific HIV diagnostic capability and potential to allow HIV recency discrimination on the same platform. Initial results show a comparable performance to the market leading incidence assay in those anti-HIV positive. However, the ability to identify Ab negative/Ag positive specimens increases the duration in which ‘true’ recent infection can be determined. This increases duration of detectable recent infection by up to two weeks but importantly identifies ‘true’ recent infections that may otherwise be discarded. Our data demonstrate that assays containing an antigen detection component are compatible with use in HIV incidence methodologies. The potential of this assay to be able to provide specific diagnostic differentiation of HIV-1 from HIV-2 and p24 Ag with modification to allow identification of recent HIV infection may change HIV diagnostic algorithms to allow the incorporation of recency testing into routine practice. 515 Western Blot Index for Estimating Recency of HIV Infection Mark Manak 1 ; Leigh . Eller 2 ; Jennifer Malia 3 ; Merlin L. Robb 2 ; Sheila Peel 2 1 Henry Jackson Fndn, Silver Spring, MD, USA; 2 US Military HIV Rsr Prog, Walter Reed Army Inst of Rsr, Silver Spring, MD, USA; 3 Walter Reed Army Inst of Rsr, Silver Spring, MD, USA Background: Estimation of time of HIV infection can be useful in epidemiological studies of incidence of infection, in establishing a link to probable risk behavior, and in narrowing the search for likely partners to whom infection could have been passed. Current HIV Recency assays such as the BED CEIA and HIV-1 Limiting Antigen (LAg)-Avidity EI A have major limitations due to variable immune response among individuals, variability in different HIV-1 subtypes, and false recency rates in some individuals. Sequential bleeds from recently HIV infected individuals exhibits progressive appearance of specific Western blot (WB) bands which can be utilized to estimate time of infection. We examined WB profiles of closely spaced bleeds from newly infected individuals from the RV217 ECHO trial to generate a WB Index (WBI) which can be useful as a measure of recency of infection. Methods: Individuals at high risk of HIV infection in Kenya, Uganda, Tanzania and Thailand were monitored twice weekly by HIV RNA Aptima assay (Hologic, LaJolla, CA), the earliest available indicator of infection.Blood from first time RNA positive individuals was collected at frequent intervals and tested by Western blot (Bio-Rad, Hercules, CA).Bands

Poster Abstracts

199

CROI 2016