Detection Of Acute HIV Infection Research Articles

B-054 Performance Evaluation of the VITROS HIV Combo Assay on the Ortho VITROS 3600 system

Abstract Background n 2014, the US CDC updated HIV screening algorithm, recommended any assay capable of reliably detecting p24 antigen and both IgG&IgM antibodies as starting point. In 2021 Chinese FDA approved VITROS HIV Combo assay as early detection of acute HIV infection with fourth-generation Ag/Ab combination test, with several declared earlier seroconversion panel reactivity than the third generation assay. This study records the experiment run to assess clinical performance using prospectively collected HIV-1 and HIV-2 antibody positive samples from Chinese CDC on the VITROS HIV Combo Assay on the VITROS 5600 Integrated System, Methods In total 450 serum/plasma samples, including 164 HIV antibody positive (162 HIV-1 antibody positive and 2 HIV-2 antibody positive) and 286 HIV negative. The HIV-2 antibody positive samples were purchased from Seracare (United States), and the remaining samples were prepared by the Chinese CDC reference laboratory. In the samples prepared in the reference laboratory, all HIV-1 antibody positive samples were tested by HIV antibody confirmation test, and the result was positive; The HIV negative samples were confirmed based on a comprehensive assessment of HIV antibodies, HIV-1 p24 antigen, HIV nucleic acid testing, and follow-up testing results, and window period has been ruled out. Ten linear and sensitivity reference samples were added to the HIV-1 p24 antigen national reference material (batch number 20190505, purchased from the China Academy of Food and Drug Control) . The antigen concentrations from L1 to L10 were 20, 10, 5, 2.5, 1.25, 0.625, 0.313, 0.156, 0.0781, and 0 IU/ml, respectively. Results The sensitivity for this positive population of samples in the VITROS Combo test was calculated as 100.00% (164/164) with an exact 95% confidence interval (Cl) of 99.26% to 100.00%. The specificity for this negative population was 99.58% (Cl 99.38%-99.73%). Conclusions The sensitivity and specificity of VITROS Combo assay are very high. With class leading antigen sensitivity doesn’t sacrifice specificity. This new assay delivers excellent confidence in results, and with more target (HIV-1 p24) being detected, can helps laboratory shortening HIV infection window, improve operators and technicians’ confidence in the outcome of HIV testing.

Impact of the 2014 CDC HIV testing guidelines on detection of acute HIV infections

The Centers for Disease Control and Prevention (CDC) issued updated guidelines for HIV testing in 2014. These guidelines recommend screening using an HIV-1/2 antigen/antibody (Ag/Ab) test and create the ability to identify algorithm-defined acute HIV infections (AHI). The guidelines also recommend laboratory confirmation of preliminary positive point of care (POC) rapid HIV test results and specimens from high-risk individuals who test POC rapid negative. The Florida Public Health Laboratory (FPHL) switched from an antibody-only algorithm to the CDC recommended algorithm April 16, 2012.To analyze the FPHL HIV testing data and evaluate the impact of the CDC recommended algorithm on the identification of AHI, time to result and inconclusive HIV reports.FPHL HIV test data, for the period January 1, 2010 through December 31, 2019, was reviewed to determine the number of AHI cases identified, the number of indeterminate HIV results and the time from specimen receipt to result for tests in the antibody-only and CDC recommended algorithms. In addition, POC rapid results were compared to laboratory-based results for AHI cases for which rapid test results were available.There was no difference in time to result between the antibody-only and CDC recommended algorithms for HIV negative specimens. The time to result for HIV-1 positive specimens decreased from an average of 5 days with the antibody-only algorithm to an average of 1 day with the CDC recommended algorithm. The average number of indeterminate results per month decreased from 6.25 per month with the antibody-only algorithm to an average of 2.5 per month using the CDC recommended algorithm. Despite HIV seropositivity decreasing by 0.5% during the study period (2012 = 3.1% [3,892/124,394]: 2019 = 2.6% [2,456/95,525]), AHI cases increased annually from a total of 4 in 2012 to over 50 in 2019 and cases were identified in 30 of 67 Florida counties. The increase in identification of AHIs is credited to educational efforts with healthcare providers to encourage further testing on individuals with risk factors for HIV and a recent POC HIV-1/2 rapid negative test result.Data indicates that performing HIV testing according to the CDC recommended algorithm decreased time to result for HIV positive results, reduced the number of indeterminate results and identified algorithm-defined AHI. In addition, laboratory-based testing is warranted for high-risk individuals who test negative by POC rapid testing.

An improved HIV antigen/antibody prototype assay for earlier detection of acute HIV infection.

Early detection of acute HIV infection by HIV antigen/antibody assays depends on antigen sensitivity. Maintaining consistently high sensitivity across diverse HIV strains is critical to ensure equal detection. The performance of an improved HIV antigen/antibody prototype, HIV Combo Next, was evaluated for detection of genetically-diverse HIV strains and seroconversion samples. Antigen sensitivity of the prototype was evaluated and compared to five FDA-approved HIV antigen/antibody assays using World Health Organization (WHO) HIV p24 antigen standard and reference panels, 17 virus isolates and 9 seroconversion panels. Antibody sensitivity and assay specificity of the prototype were also assessed with 1062 disease-staged and genotyped samples, and samples from 3000 blood donors and 955 individuals with low-risk for HIV infection. Compared with other assays evaluated, the prototype demonstrated the best analytical sensitivity for WHO antigen standard, reference panels including 12 HIV-1 variants (0.04 - 0.25 IU/ml) and one HIV-2 variant, and 17 HIV virus isolates including HIV-1 group M, N, P and O and HIV-2 (0.3 -16 pg/ml). The enhanced sensitivity was also observed for seroconversion samples, detecting more PCR-positive samples with detection up to 7 days earlier than the other assays. Improvement in antigen sensitivity did not compromise antibody sensitivity or assay specificity, detecting all HIV disease-staged and genotyped samples, with assay specificity of 99.97% for blood donors and 99.68% for the low-risk population. These data indicate that the new prototype HIV Combo Next assay will be of diagnostic value, providing improved early detection for acute HIV infection from divergent HIV strains.

Association between the cytokine storm, immune cell dynamics, and viral replicative capacity in hyperacute HIV infection

IntroductionImmunological damage in acute HIV infection (AHI) may predispose to detrimental clinical sequela. However, studies on the earliest HIV-induced immunological changes are limited, particularly in sub-Saharan Africa. We assessed the plasma cytokines kinetics, and their associations with virological and immunological parameters, in a well-characterized AHI cohort where participants were diagnosed before peak viremia.MethodsBlood cytokine levels were measured using Luminex and ELISA assays pre-infection, during the hyperacute infection phase (before or at peak viremia, 1–11 days after the first detection of viremia), after peak viremia (24–32 days), and during the early chronic phase (77–263 days). Gag-protease-driven replicative capacities of the transmitted/founder viruses were determined using a green fluorescent reporter T cell assay. Complete blood counts were determined before and immediately following AHI detection before ART initiation.ResultsUntreated AHI was associated with a cytokine storm of 12 out of the 33 cytokines analyzed. Initiation of ART during Fiebig stages I–II abrogated the cytokine storm. In untreated AHI, virus replicative capacity correlated positively with IP-10 (rho = 0.84, P < 0.001) and IFN-alpha (rho = 0.59, P = 0.045) and inversely with nadir CD4+ T cell counts (rho = − 0.58, P = 0.048). Hyperacute HIV infection before the initiation of ART was associated with a transient increase in monocytes (P < 0.001), decreased lymphocytes (P = 0.011) and eosinophils (P = 0.003) at Fiebig stages I–II, and decreased eosinophils (P < 0.001) and basophils (P = 0.007) at Fiebig stages III–V. Levels of CXCL13 during the untreated hyperacute phase correlated inversely with blood eosinophils (rho = − 0.89, P < 0.001), basophils (rho = − 0.87, P = 0.001) and lymphocytes (rho = − 0.81, P = 0.005), suggesting their trafficking into tissues. In early treated individuals, time to viral load suppression correlated positively with plasma CXCL13 at the early chronic phase (rho = 0.83, P = 0.042).ConclusionWhile commencement of ART during Fiebig stages I–II of AHI abrogated the HIV-induced cytokine storm, significant depletions of eosinophils, basophils, and lymphocytes, as well as transient expansions of monocytes, were still observed in these individuals in the hyperacute phase before the initiation of ART, suggesting that even ART initiated during the onset of viremia does not abrogate all HIV-induced immune changes.

Rapid HIV Antigen-Antibody Assays and Detection of Acute HIV Infection in Sub-Saharan Africa.

Detection of acute HIV infection is a unique problem that fourth-generation HIV assays were expected to alleviate. In this commentary, we draw attention to the limitations and challenges with use of currently available rapid antigen-antibody (Ag/Ab) combination tests for detection of acute HIV infection in sub-Saharan Africa. Laboratory-based HIV-1 Ag/Ab immunoassays are complex, requiring specialized equipment and handling that are currently not affordable in many settings in Africa. The point-of-care Ag/Ab platform on the other hand is easier to deploy and potentially more accessible in resource-limited settings. However, available fourth-generation HIV-1 rapid diagnostic tests have demonstrated poor performance characteristics in field studies where non-B subtypes of HIV-1 dominate. The potential for point-of-care HIV-1 Ag/Ab diagnostics to significantly improve detection of acute HIV infection remains yet to be realized in sub-Saharan Africa. Assay platforms need to be optimized to identify local circulating subtypes, and optimal algorithms need to be determined.

Brief Report: The Amsterdam Symptom and Risk-Based Score Predicts for Acute HIV Infection in Men Who Have Sex With Men in San Diego.

Dijkstra et al recently described a risk- and symptom-based score moderately predictive for HIV seroconversion in the preceding 6-12 months in men who have sex with men (MSM) in Amsterdam. Our objective was to determine whether this "Amsterdam Score" could also predict for acute HIV infection (AHI) in MSM. This study is a case-control analysis of a prospectively enrolled cohort of MSM who voluntarily presented for HIV testing in San Diego. The study sample was composed of MSM who screened HIV antibody-negative and then either tested positive with AHI [HIV nucleic acid test (NAT)-positive] or tested HIV NAT-negative. The Amsterdam Score was calculated for each participant in the study sample. Score performance was assessed using receiver operating characteristic curves and their area under the curve (AUC). An optimal cutoff was determined using the Youden index. Seven hundred fifty-seven MSM (110 AHI and 647 HIV NAT-negative) were included in the analysis. AHI and HIV-negative cases were similar in age [median 32 years (interquartile range 26-42) vs 33 (27-45), respectively, P = 0.082]. The Amsterdam Score yielded a receiver operating characteristic curve with an AUC of 0.88 (95% confidence interval: 0.84 to 0.91). An optimal cutoff of ≥1.6 was 78.2% sensitive and 81.0% specific. The risk- and symptom-based Amsterdam Score was highly predictive (AUC of 0.88) of AHI in MSM in San Diego. The Amsterdam Score could be used to target NAT utilization in resource-poor settings among MSM who test HIV antibody-negative, although the potential cost-savings must be balanced with the risk of missing AHI diagnoses.

A Cohort Approach to Real-Time Detection of Acute HIV Infections Among People Who Inject Drugs in St. Petersburg, Russia.

To detect acute HIV infections (AHIs) in real time among people who inject drugs (PWID) in St. Petersburg, Russia and to test the feasibility of this approach. Prospective cohort study. One hundred seronegative or acutely HIV-infected at screening PWID were enrolled and followed until the end of the 12-month pilot period. Each participant was evaluated, tested, and counseled for HIV monthly. Two HIV tests were used: HIV antibody and HIV RNA PCR. If diagnosed with AHI, participants were followed weekly for a month; then, monthly for 3 months; and then, quarterly for the duration of the follow-up period. HIV risk behavior was assessed at each study visit. Most enrolled PWID were 30-39 years old, male, completed high school or more, not employed full-time, heroin users, and frequently shared injection paraphernalia. AHI prevalence at screening was 1.8% [95% confidence interval (CI): 0.4, 5.5]. Three participants with AHI at enrollment represented 3% (95% CI: 0.6, 8.5) of the 100 participants who consented to enroll. Among the HIV-uninfected participants (n = 97), the AHI incidence over time was 9.3 per 100 person-years. Persons with AHI were more likely to report alcohol intoxication within the prior 30 days. This was the first study to detect AHI using a cohort approach. The approach proved to be feasible: recruitment, retention, AHI detection, and virological endpoints were successfully reached. A cost analysis in a real-world setting would be required to determine if this strategy could be brought to scale. The study revealed continued high HIV incidence rate among PWID in St. Petersburg, Russia and the importance of prevention and treatment programs for this group.

Performance of the BioPlex 2200 HIV Ag-Ab assay for identifying acute HIV infection

BackgroundAssays that detect HIV antigen (Ag) and antibody (Ab) can be used to screen for HIV infection. ObjectivesTo compare the performance of the BioPlex 2200 HIV Ag-Ab assay and two other Ag/Ab combination assays for detection of acute HIV infection. Study designSamples were obtained from 24 individuals (18 from the US, 6 from South Africa); these individuals were classified as having acute infection based on the following criteria: positive qualitative RNA assay; two negative rapid tests; negative discriminatory test. The samples were tested with the BioPlex assay, the ARCHITECT HIV Ag/Ab Combo test, the Bio-Rad GS HIV Combo Ag-Ab EIA test, and a viral load assay. ResultsTwelve (50.0%) of 24 samples had RNA detected only ( > 40 to 13,476 copies/mL). Ten (43.5%) samples had reactive results with all three Ag/Ab assays, one sample was reactive with the ARCHITECT and Bio-Rad assays, and one sample was reactive with the Bio-Rad and BioPlex assays. The 11 samples that were reactive with the BioPlex assay had viral loads from 83,010 to >750,000 copies/mL; 9/11 samples were classified as Ag positive/Ab negative by the BioPlex assay. ConclusionsDetection of acute HIV infection was similar for the BioPlex assay and two other Ag/Ab assays. All three tests were less sensitive than a qualitative RNA assay and only detected HIV Ag when the viral load was high. The BioPlex assay detected acute infection in about half of the cases, and identified most of those infections as Ag positive/Ab negative.

IP-10 Levels as an Accurate Screening Tool to Detect Acute HIV Infection in Resource-Limited Settings

Acute HIV infection (AHI) is the period prior to seroconversion characterized by high viral replication, hyper-transmission potential and commonly, non-specific febrile illness. AHI detection requires HIV-RNA viral load (VL) determination, which has very limited access in low-income countries due to restrictive costs and implementation constraints. We sought to identify a biomarker that could enable AHI diagnosis in scarce-resource settings, and to evaluate the feasibility of its implementation. HIV-seronegative adults presenting at the Manhiça District Hospital, Mozambique, with reported-fever were tested for VL. Plasma levels of 49 inflammatory biomarkers from AHI (n = 61) and non-HIV infected outpatients (n = 65) were determined by Luminex and ELISA. IP-10 demonstrated the best predictive power for AHI detection (AUC = 0.88 [95%CI 0.80–0.96]). A cut-off value of IP-10 ≥ 161.6 pg/mL provided a sensitivity of 95.5% (95%CI 85.5–99.5) and a specificity of 76.5% (95%CI 62.5–87.2). The implementation of an IP-10 screening test could avert from 21 to 84 new infections and save from US$176,609 to US$533,467 to the health system per 1,000 tested patients. We conclude that IP-10 is an accurate biomarker to screen febrile HIV-seronegative individuals for subsequent AHI diagnosis with VL. Such an algorithm is a cost-effective strategy to prevent disease progression and a substantial number of further HIV infections.

Comparative evaluation of three FDA-approved HIV Ag/Ab combination tests using a genetically diverse HIV panel and diagnostic specimens

BackgroundHIV Ag/Ab combination assays are recommended by CDC for routine screening and several HIV Ag/Ab combination tests are now FDA-approved. Maintaining high specificity and consistent sensitivity across diverse HIV strains is critical for these assays to accurately detect HIV infection and expedite delivery of patient results. ObjectivesTo evaluate performance of three FDA-approved HIV tests: ARCHITECT HIV Combo (Abbott), ADVIA Centaur HIV Combo (Siemens) and BioPlex HIV Ag-Ab (Bio-Rad). Study designSensitivity and specificity were evaluated using an extensive panel of 28 HIV infected human specimens and 17 cultured virus isolates representing multiple genotypes, 6 seroconversion panels, 4 human samples with acute infection, WHO p24 standard and 4020 clinical specimens. ResultsThe p24 limit of detection (LOD) for the WHO standard was 0.19IU/ml, 0.70IU/ml, and 1.77IU/ml in BioPlex, ARCHITECT, and Centaur respectively. The distribution of LODs across 15 HIV-1 isolates was substantially narrower in ARCHITECT (5–33pg/ml) than in BioPlex (11–198pg/ml) and Centaur (6–384pg/ml). All assays detected antibodies to the majority of HIV-1 and HIV-2 variants. However, reduced sensitivity was observed for Centaur in detection of antibodies to HIV-1 group M (CRF02_AG), O and N variants. BioPlex and ARCHITECT showed better seroconversion sensitivity than Centaur, detecting one bleed (3–7 days) earlier in 4 (BioPlex) and 3 (ARCHITECT) of 6 seroconversion panels. ARCHITECT demonstrated the highest specificity (99.90–100%) compared to BioPlex (99.80%) and Centaur (99.42%). ConclusionsThe overall performance of ARCHITECT and BioPlex was superior to Centaur, especially for detection of acute HIV infection.

Clinical and public health implications of acute and early HIV detection and treatment: a scoping review.

Introduction: The unchanged global HIV incidence may be related to ignoring acute HIV infection (AHI). This scoping review examines diagnostic, clinical, and public health implications of identifying and treating persons with AHI.Methods: We searched PubMed, in addition to hand-review of key journals identifying research pertaining to AHI detection and treatment. We focused on the relative contribution of AHI to transmission and the diagnostic, clinical, and public health implications. We prioritized research from low- and middle-income countries (LMICs) published in the last fifteen years.Results and Discussion: Extensive AHI research and limited routine AHI detection and treatment have begun in LMIC. Diagnostic challenges include ease-of-use, suitability for application and distribution in LMIC, and throughput for high-volume testing. Risk score algorithms have been used in LMIC to screen for AHI among individuals with behavioural and clinical characteristics more often associated with AHI. However, algorithms have not been implemented outside research settings. From a clinical perspective, there are substantial immunological and virological benefits to identifying and treating persons with AHI – evading the irreversible damage to host immune systems and seeding of viral reservoirs that occurs during untreated acute infection. The therapeutic benefits require rapid initiation of antiretrovirals, a logistical challenge in the absence of point-of-care testing. From a public health perspective, AHI diagnosis and treatment is critical to: decrease transmission via viral load reduction and behavioural interventions; improve pre-exposure prophylaxis outcomes by avoiding treatment initiation for HIV-seronegative persons with AHI; and, enhance partner services via notification for persons recently exposed or likely transmitting.Conclusions: There are undeniable clinical and public health benefits to AHI detection and treatment, but also substantial diagnostic and logistical barriers to implementation and scale-up. Effective early ART initiation may be critical for HIV eradication efforts, but widespread use in LMIC requires simple and accurate diagnostic tools. Implementation research is critical to facilitate sustainable integration of AHI detection and treatment into existing health systems and will be essential for prospective evaluation of testing algorithms, point-of-care diagnostics, and efficacious and effective first-line regimens.

Acute HIV infection detection and immediate treatment estimated to reduce transmission by 89% among men who have sex with men in Bangkok.

Introduction: Antiretroviral treatment (ART) reduces HIV transmission. Despite increased ART coverage, incidence remains high among men who have sex with men (MSM) in many places. Acute HIV infection (AHI) is characterized by high viral replication and increased infectiousness. We estimated the feasible reduction in transmission by targeting MSM with AHI for early ART.Methods: We recruited a cohort of 88 MSM with AHI in Bangkok, Thailand, who initiated ART immediately. A risk calculator based on viral load and reported behaviour, calibrated to Thai epidemiological data, was applied to estimate the number of onwards transmissions. This was compared with the expected number without early interventions.Results: Forty of the MSM were in 4th-generation AHI stages 1 and 2 (4thG stage 1, HIV nucleic acid testing (NAT)+/4thG immunoassay (IA)-/3rdG IA–; 4thG stage 2, NAT+/4thG IA+/3rdG IA–) while 48 tested positive on third-generation IA but had negative or indeterminate western blot (4thG stage 3). Mean plasma HIV RNA was 5.62 log10 copies/ml. Any condomless sex in the four months preceding the study was reported by 83.7%, but decreased to 21.2% by 24 weeks on ART. After ART, 48/88 (54.6%) attained HIV RNA <50 copies/ml by week 8, increasing to 78/87 (89.7%), and 64/66 (97%) at weeks 24 and 48, respectively. The estimated number of onwards transmissions in the first year of infection would have been 27.3 (95% credible interval: 21.7–35.3) with no intervention, 8.3 (6.4–11.2) with post-diagnosis behaviour change only, 5.9 (4.4–7.9) with viral load reduction only and 3.1 (2.4–4.3) with both. The latter was associated with an 88.7% (83.8–91.1%) reduction in transmission.Conclusions: Disproportionate HIV transmission occurs during AHI. Diagnosis of AHI with early ART initiation can substantially reduce onwards transmission.

Screening for acute HIV infection in community-based settings: Cost-effectiveness and impact on transmissions

To determine cost-effectiveness of three community-based acute HIV infection (AHI) testing algorithms compared to HIV antibody testing alone by focusing on the potential of averting new infections occurring within a one-year time horizon among men who have sex with men (MSM). Data sources for model parameters included actual cost and prevalence data derived from a community-based AHI screening program in San Diego, and published studies. Main outcome measure was costs per infection averted (IA). The lower end of the cost range of discounted lifetime costs of an HIV infection (i.e. $236,948) was used for defining cost-effectiveness. The most sensitive algorithm for AHI detection, which was based on HIV nucleic acid amplification testing, was estimated to prevent between 5 and 45 transmissions, with simulated costs per infection averted between $965 and $141,256 when compared to HIV antibody testing alone. AHI testing was cost-effective in preventing new HIV infections among at risk MSM in San Diego, and also among other MSM populations with similar HIV prevalence but lower proportions of AHI diagnoses. These results indicate that community-based AHI testing among MSM in the United States can pay for itself over the long run.

Effect of Text Message, Phone Call, and In-Person Appointment Reminders on Uptake of Repeat HIV Testing among Outpatients Screened for Acute HIV Infection in Kenya: A Randomized Controlled Trial.

BackgroundFollowing HIV-1 acquisition, many individuals develop an acute retroviral syndrome and a majority seek care. Available antibody testing cannot detect an acute HIV infection, but repeat testing after 2–4 weeks may detect seroconversion. We assessed the effect of appointment reminders on attendance for repeat HIV testing.MethodsWe enrolled, in a randomized controlled trial, 18–29 year old patients evaluated for acute HIV infection at five sites in Coastal Kenya (ClinicalTrials.gov NCT01876199). Participants were allocated 1:1 to either standard appointment (a dated appointment card) or enhanced appointment (a dated appointment card plus SMS and phone call reminders, or in-person reminders for participants without a phone). The primary outcome was visit attendance, i.e., the proportion of participants attending the repeat test visit. Factors associated with attendance were examined by bivariable and multivariable logistic regression.Principal FindingsBetween April and July 2013, 410 participants were randomized. Attendance was 41% (85/207) for the standard group and 59% (117/199) for the enhanced group, for a relative risk of 1.4 [95% Confidence Interval, CI, 1.2–1.7].Higher attendance was independently associated with older age, study site, and report of transactional sex in past month. Lower attendance was associated with reporting multiple partners in the past two months.ConclusionsAppointment reminders through SMS, phone calls and in-person reminders increased the uptake of repeat HIV test by forty percent. This low-cost intervention could facilitate detection of acute HIV infections and uptake of recommended repeat testing.Trial RegistrationClinicaltrials.gov NCT01876199

Rapid, Fully Automated Digital Immunoassay for p24 Protein with the Sensitivity of Nucleic Acid Amplification for Detecting Acute HIV Infection.

Nucleic acid testing (NAT) has become the standard for high sensitivity in detecting low levels of virus. However, adoption of NAT can be cost prohibitive in low-resource settings where access to extreme sensitivity could be clinically advantageous for early detection of infection. We report development and preliminary validation of a simple, low-cost, fully automated digital p24 antigen immunoassay with the sensitivity of quantitative NAT viral load (NAT-VL) methods for detection of acute HIV infection. We developed an investigational 69-min immunoassay for p24 capsid protein for use on a novel digital analyzer on the basis of single-molecule-array technology. We evaluated the assay for sensitivity by dilution of standardized preparations of p24, cultured HIV, and preseroconversion samples. We characterized analytical performance and concordance with 2 NAT-VL methods and 2 contemporary p24 Ag/Ab combination immunoassays with dilutions of viral isolates and samples from the earliest stages of HIV infection. Analytical sensitivity was 0.0025 ng/L p24, equivalent to 60 HIV RNA copies/mL. The limit of quantification was 0.0076 ng/L, and imprecision across 10 runs was <10% for samples as low as 0.09 ng/L. Clinical specificity was 95.1%. Sensitivity concordance vs NAT-VL on dilutions of preseroconversion samples and Group M viral isolates was 100%. The digital immunoassay exhibited >4000-fold greater sensitivity than contemporary immunoassays for p24 and sensitivity equivalent to that of NAT methods for early detection of HIV. The data indicate that NAT-level sensitivity for acute HIV infection is possible with a simple, low-cost digital immunoassay.

Development of an In-House Multiplex Nested RT-PCR Method for Detecting Acute HIV-1 Infection in High Risk Populations.

The detection of acute HIV infection (AHI) among high risk populations can help reduce secondary transmission of HIV. The nucleic acid testing (NAT) can shorten the test window period by up to 7-12 days. In this study, we describe an in-house NAT based on the multiplex nested RT-PCR method to detect the HIV RNA. We also evaluated it in a high risk cohort in Beijing. Four primer pairs were designed and evaluated for the detection of different HIV-1 subtypes in group M. Multiplex RT-PCR and nested PCR were performed. The sensitivity, specialty, primers compatibility among HIV subtypes were evaluated simultaneously. In an MSM cohort in Beijing during a 3-year period, a total of 11,808 blood samples that were negative by ELISA or indeterminate by Western blot were analyzed by this multiplex nested RT-PCR with pooling strategy. The multiplex nested RT-PCR was successfully applied for the detection of at least six HIV-1 subtypes. The sensitivity was 40 copies/ml and the specificity was 100%. A total of 29 people were tested HIV-1 positive with acute infection in a MSM cohort of Beijing during a 3 years period. This multiplex nested RT-PCR provides a useful tool for the rapid detection of acute HIV-1 infection. When used in combination with the 3(rd) generation ELISA, it can improve the detection rate of HIV infection, especially in the source limited regions.

P95 The ability of the alere™ hivcombo point-of care test to detect acute HIV infection

Background/introduction Detection of acute HIV infection is important in preventing HIV transmission and for consideration of early antiretroviral therapy. Fourth generation (4G) HIV tests detect p24 antigen and HIV antibody and should detect acute HIV infection prior to the development of antibodies. An early version fourth generation (4G) point-of-care (POCT) test demonstrated low levels of sensitivity for p24Ag. Aim(s)/objectives To assess the ability of the new Alere™ HIV Combo 4G POCT to detect p24 antigen in patients with laboratory confirmed p24 antigenaemia. Methods P24 antigen positive serum samples were tested using the Alere ™ HIV-Combo POCT and read at 20 and 40 min. One sample gave an invalid result and was excluded. P24 antigen levels from the VIDAS quantitative HIV p24 11 assay, used as routine HIV confirmatory tests by our laboratory, were recorded for comparison. Results Twenty-four out of 27 samples (89%) were p24 antigen positive at 20 min and 25/27 (93%) samples were positive at 40 min. There were two false negative samples, shown to have the lowest levels of p24 antigen (27.6 and 8.3 pg/ml) of the 27 samples. The mean p24 antigen level with the VIDAS quantitative HIV p24 11 assay for the cohort was 236.2 (Range 8.3- >400 pg/ml). The Alere ™ HIV Combo POCT detected all P24 antigen at levels >30 pg/ml. Discussion/conclusion The Alere ™ HIV Combo POCT has 89% sensitivity for p24 antigen at 20 min and 93% at 40 min. These preliminary results suggest that the new Alere ™ HIV Combo POCT may be able to detect early infection adequately.

Current Trends in the detection of Acute HIV Infection among Blood Donors: Reliability of Pooled Nucleic Acid Amplification Technology and the Need for Population Specific Algorithms: A Systematic Review

We conducted a systematic review of quantitative studies that evaluated the accuracy of nucleic acid amplification testing technologies (NAAT) compared their cost effectiveness and evaluated minipool NAAT against individual donor testing NAAT. PubMed, Cochrane and Google Scholar were used to identify relevant peer‐reviewed journal articles published in English language between 1999 (when NAAT was introduced) and 2013. MeSH key words included: Human immunodeficiency virus OR HIV AND nucleic acid amplification techniques OR pooled NAAT AND blood donors. Additional filters include: minipool-NAAT and individual donor testing-NAAT. After screening for duplication and relevance, 50 out of 4,181 articles were selected. Thirty six (36) studies which included 5 review article, 5 retrospective cohort studies, 20 cross sectional studies, 2 statistical modeling’s, 2 national guidelines and 2 prospective cohort studies were further synthesized. Articles were further sub-divided into 8 groups based their focus area which includes: prevalence, clinical sensitivity of the assay, analytical sensitivity, test technology, testing algorithm, limit of detection and cost effectiveness. Four of six studies with pool sizes of 10 to 50 donor plasmas with standard centrifugation recorded a clinical sensitivity of 100% while the remaining two whose plasma pool size of 96 and128 had sensitivities of 92.3% and 95.3%, respectively. All four studies that focused on analytical sensitivity using different samples and controls, including cadaveric samples reported 100% analytical sensitivity using various pool sizes. We recommend minipool NAAT testing after running a third generation ELISA as highly sensitive and cost effective algorithm for low income countries.

How can we better identify early HIV infections?

Detection of early HIV infections (EHIs), including acute HIV infection (AHI), is important for individual health, prevention of HIV transmission, and measurement of HIV incidence. We describe markers of EHI, diagnostic strategies for detecting these markers, and ways to incorporate these strategies into diagnostic and HIV incidence algorithms. For individual diagnosis in the USA and Europe, laboratory-based diagnostic algorithms increasingly incorporate fourth-generation HIV antigen tests, allowing for earlier detection. In some sub-Saharan African settings, symptom-based screening is being explored to identify subsets of persons at high risk for AHI. Point-of-care diagnostics designed for AHI detection are in the pipeline and, if validated, represent an opportunity for real-time AHI diagnosis. At the population level, multiassay algorithms are promising new strategies for estimating HIV incidence on the basis of several assays applied to cross-sectional samples. These algorithms can be developed to optimize performance, in addition to cost and logistical considerations. There are important recent advances in detection of EHIs at the individual and population levels. Applying optimal combinations of tests in diagnostic and HIV incidence algorithms is urgently needed to support the multiple goals derived from enhanced detection and discrimination of EHIs.

Pooled nucleic acid testing increases the diagnostic yield of acute HIV infections in a high-risk population compared to 3rd and 4th generation HIV enzyme immunoassays

ObjectivesWe compared a 3rd generation (gen) and two 4th gen HIV enzyme immunoassays (EIA) to pooled nucleic acid testing (PNAT) for the identification of pre- and early seroconversion acute HIV infection (AHI). Study Design9550 specimens from males >18 year from clinics attended by men who have sex with men were tested by Siemens ADVIA Centaur® HIV 1/O/2 (3rd gen) and HIV Combo (4th gen), as well as by Abbott ARCHITECT® HIV Ag/Ab Combo (4th gen). Third gen non-reactive specimens were also tested by Roche COBAS® Ampliprep/COBAS® TaqMan HIV-1 Test v.2 in pools of 24 samples. Sensitivity and specificity of the three EIAs for AHI detection were compared. Results7348 persons contributed 9435 specimens and had no evidence of HIV infection, 79 (94 specimens) had established HIV infection, 6 (9 specimens) had pre-seroconversion AHI and 9 (12 specimens) had early seroconversion AHI. Pre-seroconversion AHI cases were not detected by 3rd gen EIA, whereas 2/6 (33.3%) were detected by Siemens 4th gen, 4/6 (66.7%) by Abbott 4th gen and 6/6 (100%) by PNAT. All three EIAs and PNAT detected all individuals with early seroconversion AHI. Overall sensitivity/specificity for the EIAs relative to WB or NAT resolved infection status was 93.6%/99.9% for Siemens 3rd gen, 95.7%/99.7% for Siemens 4th gen and 97.9%/99.2% for Abbott 4th gen. ConclusionsWhile both 4th gen EIAs demonstrated improved sensitivity for AHI compared to 3rd gen EIA, PNAT identified more AHI cases than either 4th gen assay. PNAT is likely to remain a useful strategy to identify AHI in high-risk populations.