CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Conclusions: Pooled PCR testing for infant diagnosis of HIV can significantly reduce diagnostic costs in settings with moderate to low prevalence rates of HIV. Apart from savings on existing programmes, this may reduce barriers to introducing additional testing opportunities, either at additional sites, or at earlier time points, such as delivery for high risk pregnancies. 617 Evaluating Dried Blood Spot Performance in Assessing HIV Treatment Failure in Uganda Allen Roberts ; Herbert C. Duber; Ming Chang; Anne Gasasira; Gloria Ikilezi; Jane Achan; Joan Dragavon; Glenda Daza; Emmanuela Gakidou; RobertW. Coombs Makerere University College of Health Sciences, Kampala, Uganda Background: HIV RNA viral load (VL) testing for patients on antiretroviral therapy (ART) has increasingly been recognized as a key component of patient monitoring, even in low- resource settings. However, due to financial and technical constraints, the routine implementation of virologic testing remains rare in most sub-Saharan Africa health facilities. Dried blood spots (DBS) have emerged as a potential low-cost substitute for standard plasma assays; however, their performance in large-scale field conditions has not sufficiently been assessed. In a prospective study in Uganda, we evaluate the ability of a novel whole blood finger-prick DBS assay to detect plasma viral load measures exceeding 1000 and 5000 copies/mL. Methods: Samples were collected from over 3000 ART patients at nine hospitals and six health centers. 150-250 consecutive adult patients who presented for care and had been on treatment for a minimum of six months were recruited into the study at each facility. Whole blood samples were collected by finger prick onto DBS cards, which were dried, packaged with desiccant, and shipped to the University of Washington for analysis. Two 50- μ L DBS were eluted in 1.3-mL lysis solution, extracted by NucliSENS miniMag, and quantified using the Abbott Real Time HIV-1 m2000rt 1.0-mL protocol with a detection level of 520 copies/mL. Paired plasma samples were analyzed with the Roche COBAS AmpliPrep/COBAS TaqMan assay at Joint Clinical Research Centre facilities in Uganda. Correlations, sensitivity, specificity, and positive and negative predictive values were calculated to compare the two methods. Results: Valid DBS and plasma results were obtained for 2663 patients. The correlation between log-transformed DBS and plasma measures was 0.673. At the 1000 copies/ mL threshold, the DBS assay had 73.2% sensitivity, 97.2% specificity, 79.2% positive predictive value (PPV), and 96.1% negative predictive value (NPV). At the 5000 copies/mL threshold, DBS sensitivity was reduced to 49.5%with high specificity (99.5%), PPV (92.6%) and NPV (94.4%). Conclusions: While the assay sensitivity improved at the lower threshold (1000 copies/mL), under field conditions the method was not sufficiently accurate to substitute for plasma measurement in determining treatment failure. Possible factors associated with low sensitivity include small spot sizes and sample degradation during storage. Further Background: To determine in populations at high risk of HIV infection, whether screening of pooled anti-HIV negative specimens for HIV RNA identifies more acute infections than testing specimens by 4 th generation assays. To confirm the limitations of 3 rd generation screening in high risk populations and discuss its implications for point of care testing. Methods: Analysis involved 3570 specimens frommen who have sex with men (MSM) from two central London STI Clinics and 1837 specimens from heterosexual men of black African ethnicity from a further 2 STI clinics. All specimens had been found to be anti-HIV negative by a 3 rd generation anti-HIV assay and were aliquoted to create mini-pools of 8 specimens each. 6 mini-pools went into a Master pools which had maximum of 48 specimens. The master pools were then tested using an in-house real time quantitative taqman probe based assay targeting HIV-1 LTR and pol . Reactive pools were broken down to reveal the individual reactive specimen. Any specimens identified as HIV positive by the RNA assay but negative by the third generation ELISA assay were further tested with a 4 th generation Ag/Ab assay. Results: Of the 5407 anti-HIV negative specimens, 6 were found to be HIV RNA positive. In 3 rd generation antibody only testing the specimens were clearly negative with a range of activity of 0.041 -0.508 OD/CO. Using the 4 th generation HIV antigen/antibody combination assay all six were positive (OD/CO ranges 4.66 – 19.64). All of the six specimens came frommen who have sex with men and five of the six came from one centre. Conclusions: 4 th generation screening is the standard of care in the UK and our data does not support the development of a national scheme to screen anti-HIV negative specimens for HIV RNA. The benefits of RNA screening such as potential earlier diagnosis maybe outweighed by the increased turnaround time for pooled RNA testing and the potential loss to follow up by this delay. However, in a high throughput laboratory that screens a high incidence population, a local application of pooled RNA testing may be applicable. The increasing use of home testing and point of care tests that are often only 3 rd generation in nature is of more concern as those acutely infected, and therefore at their most infectious, may be missed and our data supports that 4 th gen formats for HIV screening programmes will avoid missing diagnosis. 619 Improved Viral Load Monitoring Capacity With Rank-Based Algorithms for Pooled Assays Tao Liu 1 ; Joseph Hogan 1 ; Renxia Huang 3 ; Rami Kantor 2 1 Brown University, Providence, RI, US; 2 Miriam Hospital, Alpert Medical School, Brown University, Providence, RI, US; 3 Fulcrum Analytics Inc, Fairfield, CT, US Background: HIV viral load (VL) monitoring is recommended globally for patients on antiretroviral therapy (ART). However, cost and infrastructure in resource limited settings (RLS) still limit widespread implementation of this guideline. VL pooling reduces the number of assays needed to ascertain individuals’ VL. However, existing pooling methods ignore information from routinely-collected clinical markers (RCMs), such as CD4 count and percent. RCMs are correlated with VL and provide valuable information that can be utilized to improve the efficiency of pooling by reducing the number of assays needed for deconvolution. Methods: We develop a deconvolution algorithm that uses RCMs to determine an optimal individual sample testing sequence for resolving a positive pool (e.g. having a detectable VL). We first use RCMs in a prediction model to estimate risk of viral failure for each sample in a positive pool. Individual samples are then assayed sequentially in a descending order of their risk scores, following a stopping algorithm that dictates whether subsequent assays of remaining samples ‘in the pool’ are needed. Using simulation models informed by clinical data, we examine the potential advantages of our approach by comparing it to (1) individual VL testing; (2) standard pooling (VL assay of pooled samples followed by VL assays of individual samples for a positive pool); and (3) algorithm-based pooling (VL assay of pooled samples, followed by sequential VL assays of individual samples and a stopping rule that depends on updated VL values for samples remaining in the pool [May et al. JAIDS 2010]). Simulations were based on data from 597 women at the Miriam Hospital HIV Clinic (Providence, USA). Markers used for risk prediction included CD4 count, CD4%, and their 6-month changes. Viral failure was defined using three VL thresholds: 150, 400, and 1000 copies/mL. Results: The cohort had a median VL 75 copies/mL (IQR 75~400), CD4 count 407 cells/ μ L (IQR 254-576), and CD4% 23 (IQR 17-30). The Table depicts the expected number of VL assays required for each method and the percent reduction in VL tests compared to individual testing. Standard deconvolution may need more assays depending on the VL threshold. Algorithm-based deconvolution reduces the number of VL tests by 18-35%; our rank-based algorithm further reduces VL assays by 26-45%. research is needed to improve assay sensitivity and develop scalable sample collection protocols. 618 Comparison of Pooled RNA and 4 th Gen Ag/Ab Testing to Identify Acute HIV Infection Gary Murphy ; Simon Carne; Bharati Patel; Elaine Mckinney; Samual Moses; Noel Gill; John Parry; JenniferTosswill Public Health England, London, United Kingdom

Poster Abstracts

390

CROI 2015