CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Conclusions: We have shown that knowledge of the S/CO ratio allows for the test result of the Abbott Combo to be used immediately in clinical decision making. Given a sufficiently high S/CO ratio, the clinician will be able to deliver a test result to the patient without waiting for further confirmatory testing with a high degree of clinical certainty. 629 Determining HIV Status of African Adults With Discordant HIV Rapid Tests Jessica M. Fogel 1 ; Estelle Piwowar-Manning 1 ; Mark A. Marzinke 1 ;William Clarke 1 ; Michal Kulich 2 ; Jessie K. Mbwambo 3 ; Linda Richter 4 ; Glenda Gray 5 ;Thomas J. Coates 6 ; Susan H. Eshleman 1 1 Johns Hopkins University School of Medicine, Baltimore, MD, US; 2 Charles University, Prague, Czech Republic; 3 Muhimbili University Teaching Hospital, Dar es Salaam, United Republic of Tanzania; 4 Universities of the Witwatersrand and KwaZulu-Natal, Durban, South Africa; 5 South African Medical Research Council, Cape Town, South Africa; 6 David Geffen School of Medicine and University of California Los Angeles Health, Los Angeles, CA, US Background: In resource-limited settings, the World Health Organization recommends using two HIV rapid tests for HIV diagnosis. If the test results are discordant, a third tie- breaker test is often used to determine HIV status. We evaluated the HIV status of adults with discordant rapid tests and evaluated the performance of different tie-breaker tests. Samples were obtained from a population-based survey (NIHM Project Accept [HPTN 043]). The frequency of discordant rapid tests in the survey was 2.1% in Tanzania and 0.3% in South Africa. Methods: Plasma samples (N=173) were classified as HIV positive or HIV negative using a rigorous testing algorithm adapted from the HIV testing algorithm currently recommended by the United States Centers for Disease Control and Prevention. The testing algorithm included two fourth-generation immunoassays (BioRad Combo assay and Abbott Combo assay), an HIV-1/HIV-2 differentiation assay, and two HIV RNA tests. Selected samples were further characterized using a panel of laboratory assays that included a qualitative assay for antiretroviral (ARV) drug detection. Sensitivity, specificity and accuracy were determined for the following tie-breaker tests: a third-generation HIV rapid test, a third-generation enzyme immunoassay (EIA), the BioRad Combo assay, and the Abbott Combo assay. Results: Twenty-nine (16.8%) of the 173 samples were classified as HIV positive. One sample was from an acute infection. Three (10.7%) of the remaining 28 HIV positive samples had detectable HIV RNA. ARV drugs were detected in only one sample (viral load: 1,280 copies/ml). Sensitivity of the tie-breaker tests was: HIV rapid test: 8.3%; third-generation EIA: 24.1%; BioRad Combo assay: 93.1%; Abbott Combo assay: 96.6%. Specificity of the tie-breaker tests was: HIV rapid test: 96.1%; third-generation EIA: 98.6%; BioRad Combo assay: 88.2%; Abbott Combo assay: 90.3%. Accuracy of the tests ranged from 79.5-91.3%. Conclusions: Significant differences were observed in the performance of tie-breaker tests for determining HIV status in individuals with discordant HIV rapid test results. Most HIV infections were missed using an HIV rapid test or third-generation EIA as a tie-breaker. In this cohort, most HIV-infected individuals with discordant HIV rapid test results were virally suppressed in the absence of ARV drugs. More rigorous testing approaches, rather than a single tie-breaker assay, may be needed to resolve the HIV status in individuals with discordant rapid test results.

Poster Abstracts

WEDNESDAY, FEBRUARY 25, 2015 Session P-M3 Poster Session

Poster Hall

2:30 pm– 4:00 pm HIV Detection, Tropism, and CD4 Measurement 630 Accuracy of POC CD4 testing using microtube capillary sampling in Botswana households Sikhulile Moyo 1 ; Lillian Okui 1 ; Hermann Bussmann 1 ; Simani Gaseitsiwe 1 ; Erik vanWidenfeldt 1 ; Molly P. Holme 2 ; Joseph Makhema 1 ; Shahin Lockman 2 ;Vladimir Novitsky 2 ; Max Essex 2 1 Botswana Harvard AIDS Institute Partnership, Gaborone, Botswana; 2 Harvard School of Public Health, Boston, MA, US Background: Point of care (POC) CD4 cell count can reduce the time to eligibility assessment for antiretroviral treatment and improve linkage to care. In a village household setting in Botswana, we evaluated the performance of field POC CD4 testing versus conventional laboratory-based flow cytometry. Methods: Capillary blood was collected by finger-prick into EDTA microtubes. Venous blood was collected by venipuncture. Both blood collection procedures were performed in households during annual surveys in the village of Mochudi, Botswana. The Alere PIMA® systemwas used for POC CD4 testing while laboratory testing was performed using BD FacsCalibur. The Bland-Altman method was used to estimate the mean bias and 95% confidence limits of agreement (LOA). Sensitivity and specificity were calculated for a threshold of 500 cells/uL CD4 cell count.

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CROI 2015