Evaluation of a rapid and simple fourth-generation HIV screening assay for qualitative detection of HIV p24 antigen and/or antibodies to HIV-1 and HIV-2

Laboratory-based evaluation of the 4th-generation AlereTM HIV Combo rapid point-of-care test

BACKGROUND

Mozambique is a high-prevalence country for HIV and early detection of new HIV infections is crucial for control of the epidemic. We aimed to evaluate the accuracy of the 4th-generation rapid diagnostic test (RDT) AlereTM HIV Combo in detecting acute and seroconverted HIV-infection, among sexually-active women attending three clinical health centers in Maputo, Mozambique.

METHODS

Women aged 14-55 years (n = 920) seeking care at the Mavalane Health Area, Maputo (February 2018-January 2019) were included, and blood specimens sampled. Sociodemographic and sexual behavior data were collected. Point-of-care HIV testing was performed using Alere DetermineTM HIV-1/2 and Uni-GoldTM HIV-1/2. All samples were also tested using Enzygnost® HIV Integral 4 and Innotest® HIV Antigen mAb in laboratory. The 4th-generation RDT AlereTM HIV Combo was evaluated on serum samples in the laboratory. Finally, Innotest® HIV Antigen mAb, Enzygnost® HIV Integral 4 (Ag/Ab), and HIV RNA quantification acted as gold standard assays in the evaluation of AlereTM HIV Combo test for HIV antigen detection (in clinical samples and in three HIV-1 seroconversion panels).

RESULTS

The antibody component of the 4th generation AlereTM HIV Combo RDT demonstrated a sensitivity and specificity of 100% examining clinical samples. However, the test did not detect HIV p24 antigen in any clinical samples, while Innotest® HIV Antigen mAb, verified by Enzygnost® HIV Integral 4 (Ag/Ab) and/or HIV RNA quantification, detected HIV antigen in six clinical samples. Furthermore, the AlereTM HIV Combo RDT had a low sensitivity in the detection of HIV p24 antigen in seroconversion panels. The HIV prevalence among the examined women was 17.8%.

CONCLUSIONS

The 4th-generation RDT AlereTM HIV Combo showed similar sensitivity to the 3rd-generation RDTs to detect seroconverted HIV-infections. However, the sensitivity for detection of HIV p24 antigen and diagnosing acute HIV infections, before seroconversion, was low. There is an urgent need to develop and evaluate simple and affordable POC tests with high sensitivity and specificity for diagnosing individuals with acute HIV infection in resource-limited settings with high HIV prevalence.

Rapid Antigen Tests during the COVID-19 Era in Korea and Their Implementation as a Detection Tool for Other Infectious Diseases

Rapid antigen tests (RATs) are diagnostic tools developed to specifically detect a certain protein of infectious agents (viruses, bacteria, or parasites). RATs are easily accessible due to their rapidity and simplicity. During the COVID-19 pandemic, RATs have been widely used in detecting the presence of the specific SARS-CoV-2 antigen in respiratory samples from suspected individuals. Here, the authors review the application of RATs as detection tools for COVID-19, particularly in Korea, as well as for several other infectious diseases. To address these issues, we present general knowledge on the design of RATs that adopt the lateral flow immunoassay for the detection of the analyte (antigen). The authors then discuss the clinical utilization of the authorized RATs amidst the battle against the COVID-19 pandemic in Korea and their role in comparison with other detection methods. We also discuss the implementation of RATs for other, non-COVID-19 infectious diseases, the challenges that may arise during the application, the limitations of RATs as clinical detection tools, as well as the possible problem solving for those challenges to maximize the performance of RATs and avoiding any misinterpretation of the test result.

Enzyme-Linked Immunosorbent Assay: Types and Applications

Enzyme-linked immunosorbent assay (ELISA) is an immunological assay widely used in basic science research, clinical application studies, and diagnostics. The ELISA technique relies on the interaction between the antigen (i.e., the target protein) versus the primary antibody against the antigen of interest. The presence of the antigen is confirmed through the enzyme-linked antibody catalysis of the added substrate, the products of which are either qualitatively detected by visual inspection or quantitatively using readouts from either a luminometer or a spectrophotometer. ELISA techniques are broadly classified into direct, indirect, sandwich, and competitive ELISA-all of which vary based on the antigens, antibodies, substrates, and experimental conditions. Direct ELISA relies on the binding of the enzyme-conjugated primary antibodies to the antigen-coated plates. Indirect ELISA introduces enzyme-linked secondary antibodies specific to the primary antibodies bound to the antigen-coated plates. Competitive ELISA involves a competition between the sample antigen and the plate-coated antigen for the primary antibody, followed by the binding of enzyme-linked secondary antibodies. Sandwich ELISA technique includes a sample antigen introduced to the antibody-precoated plate, followed by sequential binding of detection and enzyme-linked secondary antibodies to the recognition sites on the antigen. This review describes ELISA methodology, the types of ELISA, their advantages and disadvantages, and a listing of some multifaceted applications both in clinical and research settings, including screening for drug use, pregnancy testing, diagnosing disease, detecting biomarkers, blood typing, and detecting SARS-CoV-2 that causes coronavirus disease 2019 (COVID-19).

HIV Capsid Protein Genetic Diversity Across HIV-1 Variants and Impact on New Capsid-Inhibitor Lenacapavir

The HIV p24 capsid protein has an essential, structural, and functional role in the viral replication cycle, being an interesting target for vaccine design, diagnostic tests, and new antiretroviral drugs (ARVs). The HIV-1 variability poses a challenge for the accuracy and efficiency of diagnostic and treatment tools. This study analyzes p24 diversity among HIV-1 variants and within its secondary structure in HIV-1 M, O, P, and N groups. All available HIV-1 p24 nucleotide sequences were downloaded from the Los Alamos HIV Sequence Database, selecting 23,671 sequences belonging to groups O, N, P, and M (9 subtypes, 7 sub-sub types, and 109 circulating recombinant forms or CRFs). Using a bioinformatics tool developed in our laboratory (EpiMolBio program), we analyzed the amino acid conservation compared to the HXB2 subtype B reference sequence and the V-markers, or amino acid changes that were specific for each variant with at least 10 available sequences. We inferred the p24 consensus sequence for HIV-1 and for each group to analyze the overall conservation in p24 main structural regions, reporting the percentage of substitutions per variant affecting the capsid assembly and molecule-binding, including those associated with resistance to the new capsid-inhibitor lenacapavir, and the key residues involved in lenacapavir-p24 interaction, according to the bibliography. Although the overall structure of p24 was highly conserved, the conservation in the secondary structure varied between HIV-1 variants and the type of secondary structure. All HIV-1 variants presented >80% amino acid conservation vs. HXB2 reference sequence, except for group M sub-subtype F1 (69.27%). Mutants affecting the capsid assembly or lenacapavir capsid-binding were found in <1% of the p24 consensus sequence. Our study reports the HIV-1 variants carrying 14 unique single V-markers in 9/38 group M variants and the level of p24 conservation in each secondary structure region among the 4 HIV-1 groups and group M variants, revealing no natural resistance to lenacapavir in any HIV-1 variant. We present a thorough analysis of p24 variability among all HIV-1 variants circulating to date. Since p24 genetic variability can impact the viral replication cycle and the efficacy of new p24-based diagnostic, therapeutic, and vaccine strategies, conservation studies must consider all HIV-1 variants circulating worldwide.

Acute HIV infection syndrome mimicking COVID-19 vaccination side effects: a case report

Background

Symptoms of primary HIV infection, including fever, rash, and headache, are nonspecific and are often described as flu-like. COVID-19 vaccination side effects, such as fever, which occur in up to 10% of people following COVID-19 vaccination, can make the diagnosis of acute HIV infection even more challenging.

Case presentation

A 26-year-old man presented with fever and headache following COVID-19 vaccination. The symptoms were initially thought to be vaccine side effects. A diagnostic workup was conducted due to persisting fever and headache > 72 h following vaccination, and he was diagnosed with Fiebig stage II acute HIV infection, 3 weeks after having unprotected anal intercourse with another man.

Conclusion

Thorough anamnesis is key to estimating the individual risk of primary HIV infection, in patients presenting with flu-like symptoms. Early diagnosis and initiation of antiretroviral therapy is associated with better prognosis and limits transmission of the disease.

Cross-Subtype Detection of HIV-1 Capsid p24 Antigen Using a Sensitive Europium Nanoparticle Assay

Accurate and early detection of diverse HIV-1 subtypes using currently available p24 antigen assays have been a major challenge. We report the development of a sensitive time resolved fluorescence (TRF) europium nanoparticle immuno assay for cross subtype detection of p24 antigen using broadly cross-reactive antibodies. Several antibodies were tested for optimal reactivity with antigens of diverse HIV-1 subtypes and circulating recombinant forms. We tested HIV strains using this assay for sensitivity and quantification ability at the pico-gram per millilter level. We identified two broadly cross-reactive HIV-1 p24 antibodies C65690M and ANT-152, which detected all strains of HIV tested. These two antibodies also yielded a better signal to cutoff ratio for the same amount of antigen tested in comparison to a commercial assay. Using an appropriate combination of C65690M and ANT-152 p24 antibodies capable of detecting all HIV types and highly sensitive TRF-based europium nano particle assay platform, we developed a sensitive p24 antigen assay that can detect HIV infection of all HIV subtypes and may be useful in early detection.

Cell phone based colorimetric analysis for point-of-care settings

Cell phones show considerable promise for point-of-care (POC) diagnostic procedures because they are accessible, connected, and computationally powerful. Cell phone image processing methods are being developed for the detection and quantification of a wide range of targets, employing methods from microscopy to fluorescence techniques. However, most of the lab-based biological and biochemical assays still lack a robust and repeatable cell phone analogue. Existing solutions require external smartphone hardware to obtain quantitative results, imposing a design tradeoff between accessibility and accuracy. Here, we develop a cell phone imaging algorithm that enables analysis of assays that would typically be evaluated via spectroscopy. The developed technique uses the saturation parameter of hue-saturation-value color space to enable POC diagnosis. Through the analysis of over 10 000 images, we show that the saturation method consistently outperforms existing algorithms under a wide range of operating field conditions. The performance improvement is also proven analytically via the mathematic relationship between the saturation method and existing techniques. The method presented here is a step forward towards the development of POC diagnostics by reducing the required equipment, improving the limit of detection (LOD), and increasing the precision of quantitative results.

Development of a Flow-Free Magnetic Actuation Platform for an Automated Microfluidic ELISA

There is a need to create an easily deployable and point-of-care (POC) diagnostic platform for disease outbreaks and for monitoring and maintenance of chronic illnesses. Such platforms are useful in regions where access to clinical laboratories may be limited or constrained using cost-effective solutions to quickly process high numbers of samples. Using oil and water liquid–liquid interphase separation, immunoassays developed for microfluidic chips can potentially meet this need when leveraged with electromagnetic actuation and antibody-coated superparamagnetic beads. We have developed a microfluidic immunoassay detection platform, which enables assay automation and maintains successful liquid containment for future use in the field. The assay was studied through a series of magnetic and fluid simulations to demonstrate these optimizations, and an optimized chip was tested using a target model for HIV-1, the p24 capsid antigen. The use of minimal reagents further lowers the cost of each assay and lowers the required sample volume for testing (<50 μL), that can offer easy turnaround for sample collection and assay results. The developed microfluidic immunoassay platform can be easily scaled for multiplex or multi-panel specific testing at the POC.

A flow-free device is developed for automated and rapid ELISA testing at the point-of-care settings.

p24 revisited: a landscape review of antigen detection for early HIV diagnosis

: Despite major advances in HIV testing, early detection of infection at the point of care (PoC) remains a key challenge. Although rapid antibody PoC and laboratory-based nucleic acid amplification tests dominate the diagnostics market, the viral capsid protein p24 is recognized as an alternative early virological biomarker of infection. However, the detection of ultra-low levels of p24 at the PoC has proven challenging. Here we review the landscape of p24 diagnostics to identify knowledge gaps and barriers and help shape future research agendas. Five hundred and seventy-four research articles to May 2018 that propose or evaluate diagnostic assays for p24 were identified and reviewed. We give a brief history of diagnostic development, and the utility of p24 as a biomarker in different populations such as infants, the newly infected, those on preexposure prophylaxis and self-testers. We review the performance of commercial p24 assays and consider elements such as immune complex disruption, resource-poor settings, prevalence, and assay antibodies. Emerging and ultrasensitive assays are reviewed and show a number of promising approaches but further translation has been limited. We summarize studies on the health economic benefits of using antigen testing. Finally, we speculate on the future uses of high-performance p24 assays, particularly, if available in self-test format.

The fourth generation AlereTM HIV Combo rapid test improves detection of acute infection in MTN-003 (VOICE) samples

BACKGROUND

Early and accurate detection of HIV is crucial when using pre-exposure prophylaxis (PrEP) for HIV prevention to avoid PrEP initiation in acutely infected individuals and to minimize the risk of drug resistance in individuals with breakthrough infection.

OBJECTIVE

To determine if fourth-generation antigen/antibody (Ag/Ab) rapid diagnostic tests (RDT) would have detected HIV infection earlier than the third-generation RDT used in MTN-003 (VOICE).

STUDY DESIGN

5029 VOICE participants were evaluated with third-generation Alere Determine™ HIV-1/2, OraQuick ADVANCE^® Rapid HIV-1/2, Uni-Gold™ Recombigen^® HIV-1/2 and Bio-Rad GS HIV-1/2+O EIA; and fourth-generation Alere Determine™ HIV-1/2 Ag/Ab Combo, Conformité Européene (CE)-Marked Alere™ HIV Combo and Bio-Rad HIV Combo Ag/Ab EIA. Multispot^®, GS HIV-1 Western Blot (WB) and Geenius™ (Bio-Rad) were also evaluated.

RESULTS

Of 57 antibody-negative pre-seroconversion plasma samples with HIV RNA >20 copies/mL identified, 16 (28%) were reactive by CE-Marked Alere™ HIV Combo (1 Ab; 9 Ag; 6 Ag/Ab reactive) and 4 (7%) by Alere Determine™ HIV-1/2 Ag/Ab Combo (2 Ab; 2 Ag; 0 Ag/Ab reactive) (p=0.0005). Multispot^® confirmed only 1 of 16 acute infections while WB and Geenius™ confirmed none. GS HIV Combo Ag/Ab EIA identified 27 of 57 (47%) pre-seroconversion RNA-positive samples.

CONCLUSION

In VOICE, 28% of infections missed by current third-generation RDT would have been identified with the use of CE-Marked Alere™ HIV Combo. Geenius™, Multispot^® and WB were all insensitive (<10%) in confirming infections detected by fourth-generation assays. An improved diagnostic algorithm that includes a fourth-generation RDT with HIV RNA testing will be essential for efficiently identifying seroconverters on PrEP.

Performance evaluation of the FDA-approved Determine™ HIV-1/2 Ag/Ab Combo assay using plasma and whole blood specimens

BACKGROUND

The Determine™ HIV-1/2 Ag/Ab Combo (DC) rapid test can identify HIV-1 infection earlier than rapid antibody-only tests in plasma specimens.

OBJECTIVES

We compared the performance of DC with a laboratory-based antigen/antibody (Ag/Ab) combo assay in plasma and evaluated antigen reactivity in whole blood specimens.

STUDY DESIGN

We tested by DC 508 plasma specimens collected in a prospective study and 107 sequential plasma and simulated whole blood specimens from 20 seroconversion panels. Previous results using the ARCHITECT (ARC) Ag/Ab combo assay were compared to DC results. In seroconversion panels, the days from the first HIV1 RNA-positive test to first DC-reactive in plasma and whole blood was compared. McNemar's and Wilcoxon signed rank tests were used for statistical analysis.

RESULTS

Of 415 HIV-positive samples, ARC detected 396 (95.4%) and DC 337 (81.2%) (p<0.0001). DC was reactive in 50.0% of ARC-reactive/MS-negative, 78.6% of ARC-reactive/MS-indeterminate, and 99.6% of ARC-reactive/MS-HIV-1-positive or -undifferentiated specimens. DC antigen reactivity was higher among ARC-reactive/MS-negative than MS-indeterminate samples. In 20 HIV-1 seroconversion panels, there was a significant difference between DC reactivity in plasma (91.1%) and whole blood (56.4%) (p<0.0001). DC with whole blood showed a significant delay in reactivity compared to plasma (p=0.008).

CONCLUSIONS

In plasma, DC was significantly less sensitive than an instrumented laboratory-based Ag/Ab combo assay. DC in plasma was significantly more sensitive compared to whole blood in early HIV-1 infections. With the U.S. laboratory-based diagnostic algorithm, DC as the first step would likely miss a high proportion of HIV-1 infections in early stages of seroconversion.

Seroprevalence, cost per donation and reduction in blood supply due to positive and indeterminate results for infectious markers in a blood bank in Lima, Peru

Introduction

Safety in Transfusion Medicine is subject to regulations and government legislation within a total quality framework. The aim of this study was to evaluate the impact of seroprevalence and indeterminate results on lost units and cost per donation.

Methods

A prospective cross-sectional study was performed in the Blood Bank and Transfusion Therapy Department of the Hospital Central de la Policia Nacional del Perú in Lima, Peru. All completed donations (replacement/voluntary) without complications were included in this study. Every donation met the institutional requirements and quality criteria of Programa Nacional de Hemoterapia y Bancos de Sangre (PRONAHEBAS). Data analysis was achieved using the Statistical Package for the Social Sciences.

Results

A total of 7723 donations were evaluated during 2014 and 2015 with 493 being seropositive (overall prevalence 5.25%) and 502 having indeterminate results (overall prevalence 5.35%). Thus total loss was 995 units, 437.8 L of blood and 49,750 US dollars. The most common seropositive infectious markers were the core antibody of hepatitis B virus (2.82%) and syphilis (1.02%), and the most common indeterminate results were Chagas disease (1.27%) and the core antibody of hepatitis B virus (1.26%). There was no significant change in the prevalence of seropositivity (p-value = 0.243) or indeterminate results (p-value = 0.227) over the two-year period of the study. A statistical correlation was found between the cost per lost donation and the most prevalent markers (rho = 0.848; p-value = <0.001).

Conclusion

Seroprevalence was lower than the regional mean, but the prevalence of indeterminate results was elevated causing a great impact on blood supply and economic losses to this institution.

The performance of the Alere HIV combo point-of-care test on stored serum samples; useful for detection of early HIV-1 infections?

INTRODUCTION

The Alere HIV-1/2 Antigen/Antibody Combo point-of-care test is a commercially available 4th-generation rapid test for the diagnosis of HIV infection, including acute infection. We evaluated the sensitivity of this test in samples from patients with acute, recent or chronic HIV-1 infection.

METHODS

A validation of the test was performed using 89 HIV-positive serum samples collected in 2008-2016, that were stored at -20°C. Twenty-three samples were only p24-positive (acute infection); 49 samples were antibody-positive and p24-positive (recent infection); 17 samples were only antibody-positive (chronic infection). HIV infection was confirmed by standard-of-care assays and PCR. Samples came from patients attending an outpatient clinic for STDs at the Public Health Department and from patients within the Erasmus Medical Center, Rotterdam, the Netherlands.

RESULTS

The overall sensitivity of the test for diagnosing HIV infection based on detection of p24 antigen and/or antibodies was 92% (95% CI 86% to 98%) (82/89). In acute sera with only p24 antigen positivity, the sensitivity of the test decreased to 65% (95% CI 46% to 85%) (15/23). When both antibody and antigen testing were positive, the p24 sensitivity was only 24% (95% CI 12% to 36%) (12/49), but in these sera the final test result was positive in all sera (49/49) due to the positive antibody component.

CONCLUSIONS

In a laboratory setting, this test has an overall sensitivity of 92% to detect any stage of HIV-1 infection using sera specimens. It performs relatively well in detecting early HIV and may be beneficial as an initial screening in patients with a recent exposure to HIV. Additional testing in a laboratory setting remains mandatory as a proportion of acute HIV-1 infections are missed with this test.

Rapid and sensitive detection of HIV-1 p24 antigen by immunomagnetic separation coupled with catalytic fluorescent immunoassay

In this study, a system of magnetic beads (MBs) coupled with catalytic fluorescent immunoassay for rapid and sensitive determination of HIV-1 capsid antigen p24 was developed. p24 was captured by antibody immobilized MBs, and the detection antibody was linked to horseradish peroxidase (HRP) through biotin-streptavidin recognition, catalyzing the oxidation of o-phenylenediamine (OPD) and hydrogen peroxide to produce a fluorescent product. This is the first reported utilization of the fluorescence of OPD oxidation product catalyzed by HRP for immunoassay. Optimization of conditions afforded a low detection limit of 0.5 pg/mL (3σ) for p24 with a linear range of 1.4-90.0 pg/mL. The assay exhibited good reproducibility with a relative standard deviation (RSD) of 4.4 %, 4.7 %, and 5.0 % for detecting 1.4 pg/mL, 22.5 pg/mL, and 45.0 pg/mL p24, respectively. The assay can be completed in less than 90 min. Moreover, the proposed method was successfully applied to detect p24 in spiked serum. This method overcomes the interference of MBs to the fluorescence signal and demonstrated higher sensitivity for detection of p24 than conventional ELISA kits. The system could be applied for detecting other antigens with high sensitivity, rapidity, specificity, and simple operation. Graphical Abstract A rapid and sensitive biosensing method coupling immunomagnetic separation and catalytic fluorescence for determination of HIV-1 p24 has been developed.

Evaluation of a Rapid Point of Care Test for Detecting Acute and Established HIV Infection, and Examining the Role of Study Quality on Diagnostic Accuracy: A Bayesian Meta-Analysis

Introduction

Fourth generation (Ag/Ab combination) point of care HIV tests like the FDA-approved Determine HIV1/2 Ag/Ab Combo test offer the promise of timely detection of acute HIV infection, relevant in the context of HIV control. However, a synthesis of their performance has not yet been done. In this meta-analysis we not only assessed device performance but also evaluated the role of study quality on diagnostic accuracy.

Methods

Two independent reviewers searched seven databases, including conferences and bibliographies, and independently extracted data from 17 studies. Study quality was assessed with QUADAS-2. Data on sensitivity and specificity (overall, antigen, and antibody) were pooled using a Bayesian hierarchical random effects meta-analysis model. Subgroups were analyzed by blood samples (serum/plasma vs. whole blood) and study designs (case-control vs. cross-sectional).

Results

The overall specificity of the Determine Combo test was 99.1%, 95% credible interval (CrI) [97.3–99.8]. The overall pooled sensitivity for the device was at 88.5%, 95% [80.1–93.4]. When the components of the test were analyzed separately, the pooled specificities were 99.7%, 95% CrI [96.8–100] and 99.6%, 95% CrI [99.0–99.8], for the antigen and antibody components, respectively. Pooled sensitivity of the antibody component was 97.3%, 95% CrI [60.7–99.9], and pooled sensitivity for the antigen component was found to be 12.3%, 95% (CrI) [1.1–44.2]. No significant differences were found between subgroups by blood sample or study design. However, it was noted that many studies restricted their study sample to p24 antigen or RNA positive specimens, which may have led to underestimation of overall test performance. Detection bias, selection (spectrum) bias, incorporation bias, and verification bias impaired study quality.

Conclusions

Although the specificity of all test components was high, antigenic sensitivity will merit from an improvement. Besides the accuracy of the device itself, study quality, also impacts the performance of the test. These factors must be kept in mind in future evaluations of an improved device, relevant for global scale up and implementation.

Field accuracy of fourth-generation rapid diagnostic tests for acute HIV-1: a systematic review

INTRODUCTION

Fourth-generation HIV-1 rapid diagnostic tests (RDTs) detect HIV-1 p24 antigen to screen for acute HIV-1. However, diagnostic accuracy during clinical use may be suboptimal.

METHODS

Clinical sensitivity and specificity of fourth-generation RDTs for acute HIV-1 were collated from field evaluation studies in adults identified by a systematic literature search.

RESULTS

Four studies with 17 381 participants from Australia, Swaziland, the United Kingdom and Malawi were identified. All reported 0% sensitivity of the HIV-1 p24 component for acute HIV-1 diagnosis; 26 acute infections were missed. Specificity ranged from 98.3 to 99.9%.

CONCLUSION

Fourth-generation RDTs are currently unsuitable for the detection of acute HIV-1.

How can we better identify early HIV infections?

PURPOSE OF REVIEW

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.

RECENT FINDINGS

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.

SUMMARY

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.

Detection of Acute HIV-1 Infection by RT-LAMP

A rapid, cost-effective diagnostic test for the detection of acute HIV-1 infection is highly desired. Isothermal amplification techniques, such as reverse-transcription loop-mediated isothermal amplification (RT-LAMP), exhibit characteristics that are ideal for the development of a rapid nucleic acid amplification test (NAAT) because they are quick, easy to perform and do not require complex, dedicated equipment and laboratory space. In this study, we assessed the ability of the HIV-1 RT-LAMP assay to detect acute HIV infection as compared to a representative rapid antibody test and several FDA-approved laboratory-based assays. The HIV-1 RT-LAMP assay detected seroconverting individuals one to three weeks earlier than a rapid HIV antibody test and up to two weeks earlier than a lab-based antigen/antibody (Ag/Ab) combo enzyme immunoassay (EIA). RT-LAMP was not as sensitive as a lab-based qualitative RNA assay, which could be attributed to the significantly smaller nucleic acid input volume. To our knowledge, this is the first demonstration of detecting acute HIV infection using the RT-LAMP assay. The availability of a rapid NAAT, such as the HIV-1 RT-LAMP assay, at the point of care (POC) or in laboratories that do not have access to large platform NAAT could increase the percentage of individuals who receive an acute HIV infection status or confirmation of their HIV status, while immediately linking them to counseling and medical care. In addition, early knowledge of HIV status could lead to reduced high-risk behavior at a time when individuals are at a higher risk for transmitting the virus.

Rapid HIV Testing Is Highly Acceptable and Preferred among High-Risk Gay And Bisexual Men after Implementation in Sydney Sexual Health Clinics

BACKGROUND

Rapid HIV testing (RHT) is well established in many countries, but it is new in Australia. We assessed the acceptability of RHT and its associations among gay, bisexual and other men who have sex with men (GBM) after implementation of RHT in Sydney sexual health clinics.

METHODS

GBM were invited to complete an acceptability questionnaire before and after provision of the result of finger-prick blood RHT, comparing their experience of RHT with conventional HIV testing (CHT) involving venipuncture. Logistic regression was used to assess associations between patient characteristics and the preference for RHT over CHT next time they tested for HIV.

RESULTS

Of 1061 GBM who received non-reactive RHT results, 59% found RHT less stressful than CHT and 34% reported no difference, and 61% found RHT more comfortable than CHT and 26% reported no difference. Nearly all men were satisfied with RHT result delivery (99%) and the RHT process overall (99%). Most men (79%) preferred RHT for their next HIV test and this preference was stronger in men who were aged 35-44 years (adjusted odds ratio [AOR] 2.49, p<0.01), reported they would test more often if RHT was available (AOR 1.66, p=0.01), found returning for results annoying (AOR 1.67, p=0.01), and found RHT less stressful (AOR 2.37, p<0.01) and more comfortable (AOR 1.62, p=0.02) than CHT. Men concerned about the reliability of RHT were less than half as likely to prefer RHT for their next HIV test (AOR 0.44, p<0.01).

CONCLUSIONS

Most GBM preferred RHT to CHT next time and this preference was associated with finding RHT more convenient, more comfortable and less stressful than CHT. These findings suggest that in a clinic setting RHT should be considered to improve the patient experience and may potentially increase uptake and frequency of HIV testing.

Development and implementation challenges of a quality assured HIV infant diagnosis program in Nigeria using dried blood spots and DNA polymerase chain reaction

Nigeria has one of the highest HIV burdens as well as mother-to-infant transmission rates in the world. A pilot program using polymerase chain reaction (PCR)-based testing of dried blood spot (DBS) specimens was implemented to enable early identification of HIV-infected infants and timely referral and linkage to care. From February 2007 to October 2008, whole blood was collected by finger prick to prepare DBS from infants <18 months presenting in six public mother-and-child health facilities in Lagos, Nigeria. The DBS were tested using the Roche Amplicor HIV-1 DNA Test, v1.5. To monitor laboratory testing quality, all of the PCR-positive and 10% of the PCR-negative DBS were retested by the same method at another reference laboratory. Three hundred and sixty-five randomly selected infants were screened using HIV rapid tests (RT) according to the national algorithm and RT-negative and PCR-positive specimens were also tested using Genscreen enzyme-linked immunosorbent assay (EIA) (Bio-Rad, France). The turnaround time (TAT) from sample collection, testing, and dispatching of results from each health facility was monitored. A total of 1,273 infants with a median age of 12.6 weeks (1 day to 71.6 weeks) participated in the program and 280 (22.0%) were PCR positive. HIV transmission levels varied greatly in the different health facilities ranging from 7.1% to 38.4%. Infants aged 48 to 72 weeks had the highest level of PCR positivity (41.1%). All PCR-positive specimens were confirmed by retesting. The mean turnaround time from DBS collection to returning of the laboratory result to the health facilities was 25 days. Three infants were found to be HIV antibody negative by rapid tests but were positive by both PCR and the fourth generation EIA. The DBS-based PCR program accurately identified all of the HIV-infected infants. However, many programmatic challenges related to the laboratory and TAT were identified.

Effect of testing experience and profession on provider acceptability of rapid HIV testing after implementation in public sexual health clinics in Sydney

OBJECTIVES

Rapid HIV testing (RHT) is well established in many countries, but it is new in Australia since a policy change in 2011. We assessed service provider acceptability of RHT before and after its implementation in four Sydney public sexual health clinics.

METHODS

Service providers were surveyed immediately after training in RHT and again 6-12 months later. Differences in mean scores between survey rounds were assessed via t-tests, with stratification by profession and the number of tests performed.

RESULTS

RHT was rated as highly acceptable among staff at baseline and acceptability scores improved between survey rounds. Belief in being sufficiently skilled and experienced to perform RHT (P = 0.004) and confidence in the delivery of nonreactive results increased (P = 0.007), while the belief that RHT was disruptive declined (P = 0.001). Acceptability was higher for staff who had performed a greater number of tests regarding comfort with their role in RHT (P = 0.004) and belief that patients were satisfied with RHT (P = 0.007). Compared with nurses, doctors had a stronger preference for a faster rapid test (P = 0.027) and were more likely to agree that RHT interfered with consultations (P = 0.014).

CONCLUSIONS

Differences in responses between professions may reflect differences in staff roles, the type of patients seen by staff and the model of testing used, all of which may affect the number of tests performed by staff. These findings may inform planning for how best to implement RHT in clinical services.

Poor performance of the determine HIV-1/2 Ag/Ab combo fourth-generation rapid test for detection of acute infections in a National Household Survey in Swaziland

Fourth-generation HIV rapid tests (RTs) claim to detect both p24 antigen (Ag) and HIV antibodies (Ab) for early identification of acute infections, important for targeting prevention and reducing HIV transmission. In a nationally representative household survey in Swaziland, 18,172 adults, age 18 to 49 years, received home-based HIV rapid testing in 2010 and 2011. Of the 18,172 individuals, 5,822 (32.0%) were Ab positive (Ab(+)) by the Determine HIV-1/2 Ab/Ab combo test, and 5,789 (99.4%) of those were confirmed to be reactive in the Uni-Gold test. Determine combo identified 12 individuals as having acute infections (Ag(+)/Ab negative [Ab(-)]); however, none had detectable HIV-1 RNA and 8 of 12 remained HIV negative at their 6-week follow-up visit (4 were lost to follow-up). All RT-nonreactive samples were pooled and tested by nucleic acid amplification testing (NAAT) to identify acute infections. NAAT identified 13 (0.1%) of the 12,338 HIV antibody-negative specimens as HIV RNA positive, with RNA levels ranging from 300 to >10,000,000 copies/ml. However, none of them were Ag(+) by Determine combo. Follow-up testing of 12 of the 13 NAAT-positive individuals at 6 months demonstrated 12 seroconversions (1 individual was lost to follow-up). Therefore, the Determine combo test had a sensitivity of 0% (95% confidence interval, 0 to 28) and positive predictive value of 0% for the detection of acute infections. The ability of the 4th-generation Determine combo to detect antigen was very poor in Swaziland. Thus, the Determine combo test does not add any value to the current testing algorithm; rather, it adds additional costs and complexity to HIV diagnosis. The detection of acute HIV infections may need to rely on other testing strategies.

Multi-centre evaluation of the Determine HIV Combo assay when used for point of care testing in a high risk clinic-based population

Background

Determine HIV Combo (DHC) is the first point of care assay designed to increase sensitivity in early infection by detecting both HIV antibody and antigen. We conducted a large multi-centre evaluation of DHC performance in Sydney sexual health clinics.

Methods

We compared DHC performance (overall, by test component and in early infection) with conventional laboratory HIV serology (fourth generation screening immunoassay, supplementary HIV antibody, p24 antigen and Western blot tests) when testing gay and bisexual men attending four clinic sites. Early infection was defined as either acute or recent HIV infection acquired within the last six months.

Results

Of 3,190 evaluation specimens, 39 were confirmed as HIV-positive (12 with early infection) and 3,133 were HIV-negative by reference testing. DHC sensitivity was 87.2% overall and 94.4% and 0% for the antibody and antigen components, respectively. Sensitivity in early infection was 66.7% (all DHC antibody reactive) and the DHC antigen component detected none of nine HIV p24 antigen positive specimens. Median HIV RNA was higher in false negative than true positive cases (238,025 vs. 37,591 copies/ml; p = 0.022). Specificity overall was 99.4% with the antigen component contributing to 33% of false positives.

Conclusions

The DHC antibody component detected two thirds of those with early infection, while the DHC antigen component did not enhance performance during point of care HIV testing in a high risk clinic-based population.

Point of Care Technologies for HIV

Effective prevention of HIV/AIDS requires early diagnosis, initiation of therapy, and regular plasma viral load monitoring of the infected individual. In addition, incidence estimation using accurate and sensitive assays is needed to facilitate HIV prevention efforts in the public health setting. Therefore, more affordable and accessible point-of-care (POC) technologies capable of providing early diagnosis, HIV viral load measurements, and CD4 counts in settings where HIV is most prevalent are needed to enable appropriate intervention strategies and ultimately stop transmission of the virus within these populations to achieve the future goal of an AIDS-free generation. This review discusses the available and emerging POC technologies for future application to these unmet public health needs.

Rapid HIV testing increases the rate of HIV detection in men who have sex with men: using rapid HIV testing in a primary care clinic

Rapid HIV testing was approved in Australia in December 2012. Data was collected to describe the early experience of using rapid testing in Australia but as the information was collected, the authors noted that there appeared to be a high rate of HIV diagnoses amongst rapid testers. Further analysis confirmed this impression, when the rate was compared to a baseline rate of HIV diagnoses over the 32 months before the rapid testing started (4.1% vs 1.3%).

A novel time-limited pop-up HIV testing service for gay men in Sydney, Australia, attracts high-risk men

Background HIV diagnoses have been increasing steadily in Australia and are concentrated among gay, bisexual and other men who have sex with men (GBM). HIV testing is a key control strategy, and in 2013, a novel time-limited pop-up community HIV testing service (Pop-up) was introduced to raise awareness and increase testing options for GBM. The Pop-up service offered rapid HIV tests only. We compared uptake and outcomes of the Pop-up service to an established clinical model [a fast-track screening service in a sexual health clinic offering rapid and/or conventional HIV tests and sexually transmissible infection (STI) tests].

METHODS

Service delivery data was collated and analysed from the HIV Pop-up (25 November to 1 December 2013) and the fast-track HIV/STI screening service (Xpress) in a sexual health clinic immediately before the Pop-up (1 August to 22 November 2013). A comparison of all the HIV tests and results, tests per hour and characteristics of new clients (demographics, risk behaviour, testing history) was conducted using χ(2), Poisson distribution and Ranksum tests.

RESULTS

At the Pop-up service, 182 GBM had a rapid HIV test conducted over the 5-day period (average: seven HIV tests per hour) and no HIV tests were reactive (0%, 95% confidence interval: 0-1.8%). At the Xpress service, 1075 asymptomatic GBM had at least one STI test and 957 GMB had a HIV test (rapid or conventional) conducted over the 3-month period (average: four HIV tests per hour), with two positive HIV tests (0.2%, 95% confidence interval: 0.02-0.7) and 151 positive STI tests (14%, 95% confidence interval: 12-16.2). Compared with new patients at the Xpress service, GBM attending the Pop-up service were older (median of 39 vs 29 years, P<0.01); more likely to report ≥5 sexual partners in the past 3 months (P=0.02); more likely to reside in 'Gay Sydney' (P<0.01); and more likely to be tested for HIV (P<0.01).

CONCLUSIONS

Time-limited Pop-up community HIV testing is feasible and reached high-risk GBM, but compared with a clinic-based model, it only reached a smaller proportion of GBM who test infrequently or who have never been tested and are unaware of their HIV status. No STI testing was conducted through the Pop-up service, which allowed a higher throughput of HIV tests; however, a significant number of STIs may have been missed.

Performance of the Alere Determine™ HIV-1/2 Ag/Ab Combo Rapid Test with specimens from HIV-1 seroconverters from the US and HIV-2 infected individuals from Ivory Coast

BACKGROUND

FDA-approved HIV Antigen/Antibody combo (4th generation) immunoassays (IAs) can identify HIV-1 infections before the Western blot (WB) becomes positive. In the US, increased detection of acute HIV infections has been facilitated by using 4th generation IAs, but there is no FDA-approved 4th generation rapid test (RT). The Alere Determine™ HIV-1/2 Ag/Ab Combo (Determine Combo) RT detects and distinguishes HIV p24 Antigen (Ag) from Antibody (Ab) to HIV-1+HIV-2 and thus has the potential to improve diagnosis of acute HIV infection.

OBJECTIVE

To evaluate the ability of Determine Combo RT to detect acute/early HIV-1 infections and HIV-2 antibody in well-characterized plasma specimens.

STUDY DESIGN

In HIV-1 seroconverters from the US, Determine Combo reactivity was evaluated by performing the 50% cumulative frequency analysis and by comparing with 3rd and 4th generation IAs' reactivity. HIV-2 plasma specimens from Ivory Coast were tested with Determine Combo.

RESULTS

The 50% cumulative frequency analysis in 17 seroconverters placed Determine Combo (Ag+/Ab-, Ag+Ab+, Ag-/Ab+) and Ab-component reactivity at 15.5 and 7 days before WB positivity, respectively. In 26 seroconverters, Determine Combo was reactive in 99.0% and 92.5% of 3rd and 4th generation IAs-reactive specimens, respectively. All HIV-2 plasma specimens were Ab-reactive/Ag-non-reactive by Determine Combo.

CONCLUSIONS

Based on previous results with the same seroconversion panels, combined Ag/Ab reactivity of the Determine Combo appears between FDA-approved 4th and 3rd generation laboratory IAs. These data indicate that this RT could detect HIV-1 infection earlier than other RTs and it performs well in HIV-2 specimens.

Reduction of the HIV seroconversion window period and false positive rate by using ADVIA Centaur HIV antigen/antibody combo assay

Background

Early diagnosis of HIV infection reduces morbidity and mortality. Fourth-generation HIV detection assays are more sensitive because they can detect p24 antigen as well as anti-HIV antibodies. In this study, we evaluated the performance of a new fourth-generation ADVIA Centaur HIV antigen/antibody combo (CHIV) assay (Siemens Healthcare Diagnostics Inc., USA) for early detection of HIV infection and reduction of false positive rate.

Methods

Four seroconversion panels were included. The third-generation ADVIA Centaur HIV 1/O/2 enhanced (EHIV) assay (Siemens Healthcare Diagnostics Inc., USA) and fourth-generation CHIV assay were used to test each panel for HIV infection. The presence of antigen was confirmed using HIV p24 antigen assay. To evaluate false-positivity and specificity, 54 HIV false-positive and HIV-negative serum samples from 100 hospitalized patients and 600 healthy subjects were included.

Results

Compared to the EHIV assay, the CHIV assay had a shorter window for three of the seroconversion panels: a difference of 10 days and two bleeds in one panel, and 4 days and one bleed in the other two panels. Only 34 of the 54 (63%) samples known to yield false-positive results by EHIV assay had repeatedly yielded reactive results in the CHIV assay. One of the 600 healthy subjects had a false-positive result with the CHIV assay; thus, the specificity was 99.85% (699/700). CHIV accurately determined the reactive results for the HIV-confirmed serum samples from known HIV patients and Korea Food & Drug Administration (KFDA) panels.

Conclusions

The new fourth-generation ADVIA Centaur HIV assay is a sensitive and specific assay that shortens the serological window period and allows early diagnosis of HIV infection.

Finding those at risk: acute HIV infection in Newark, NJ

BACKGROUND

A screening strategy combining rapid HIV-1/2 (HIV) antibody testing with pooled HIV-1 RNA testing increases identification of HIV infections, but may have other limitations that restrict its usefulness to all but the highest incidence populations.

OBJECTIVE

By combining rapid antibody detection and pooled nucleic acid amplification testing (NAAT) testing, we sought to improve detection of early HIV-1 infections in an urban Newark, NJ hospital setting.

STUDY DESIGN

Pooled NAAT HIV-1 RNA testing was offered to emergency department patients and outpatients being screened for HIV antibodies by fingerstick-rapid HIV testing. For those negative by rapid HIV and agreeing to NAAT testing, pooled plasma samples were prepared and sent to the University of Washington where real-time reverse transcription-polymerase chain reaction (RT-PCR) amplification was performed.

RESULTS

Of 13,226 individuals screened, 6381 had rapid antibody testing alone, and 6845 agreed to add NAAT HIV screening. Rapid testing identified 115 antibody positive individuals. Pooled NAAT increased HIV-1 case detection by 7.0% identifying 8 additional cases. Overall, acute HIV infection yield was 0.12%. While males represent only 48.1% of those tested by NAAT, all samples that screened positive for HIV-1 RNA were obtained from men.

CONCLUSION

HIV-1 RNA testing of pooled, HIV antibody-negative specimens permits identification of recent infections. In Newark, pooled NAAT increased HIV-1 case detection and provided an opportunity to focus on treatment and prevention messages for those most at risk of transmitting infection. Although constrained by client willingness to participate in testing associated with a need to return to receive further results, use of pooled NAAT improved early infection sensitivity.

Performance evaluation of a new fourth-generation HIV Ag/Ab combination electrochemiluminescence immunoassay – evaluation of a new HIV assay

A new fourth-generation HIV Ag/Ab electrochemiluminescence immunoassay for screening of HIV infection, the Elecsys® HIV Combi PT (Roche Diagnostics, Penzberg, Germany) assay, is going to be commercially available in clinical laboratories in China. This assay was evaluated and compared with two commonly used assays: Elecsys® HIV Combi assay and the Livzon anti-HIV-1/2 ELISA. Commercially available panels and 30 established HIV infection samples were tested to evaluate the sensitivity. In addition, a total of 675 routine clinical samples were collected and tested in West China Hospital to compare the specificity. Any reactive result from a screening test was retested and all reactive retested samples were confirmed with Western blot assay, Elecsys® HIV Ag test, Elecsys® HIV Ag confirmatory test or HIV-1 RNA NAT testing. According to the results of the HIV seroconversion panels, the Elecsys® HIV Combi PT could detect seroconversion at the same bleed or at least one bleed earlier compared to the other two assays. Among the 675 clinical samples, most results were consistent except for one specimen with a false-negative result using Elecsys® HIV Combi assay. In conclusion, the Elecsys® HIV Combi PT has shown satisfactory sensitivity and specificity to be a screening test for HIV infection.

RAPID HOME-BASED HIV TESTING TO REDUCE COSTS IN A LARGE TUBERCULOSIS COHORT STUDY

To reduce costs in a large tuberculosis household contact cohort study in Lima, Peru, we replaced laboratory-based HIV testing with home-based rapid testing. We developed a protocol and training course to prepare staff for the new strategy; these included role playing for home-based deployment of the Determine® HIV 1/2 Ag/Ac Combo HIV test. Though the rapid HIV test produced more false-positives, the overall cost per participant tested, refusal rate and time to confirmatory HIV testing were lower with the home-based rapid testing strategy compared to the original approach. Rapid testing could be used in similar research or routine care settings.

Performance of the first fourth-generation rapid human immunodeficiency virus test in children

Diagnosing HIV infection in infants by p24 antigen detection at point of care is likely to reduce infant morbidity and mortality. A fourth-generation rapid test evaluated on 202 stored samples from children of known age and clinical presentation demonstrated a sensitivity of <2% for detecting p24 antigen in 61 HIV-infected infants and demonstrated 100% sensitivity and specificity for detecting HIV antibodies in infants aged 6 months and younger.

Low-cost tools for diagnosing and monitoring HIV infection in low-resource settings

Low-cost technologies to diagnose and monitor human immunodeficiency virus (HIV) infection in developing countries are a major subject of current research and health care in the developing world. With the great need to increase access to affordable HIV monitoring services in rural areas of developing countries, much work has been focus on the development of point-of-care technologies that are affordable, robust, easy to use, portable and of sufficient quantitative accuracy to enable clinical decision-making. For diagnosis of HIV infection, some low-cost tests, such as lateral flow tests and enzyme-linked immunosorbent assays, are already in place and well established. However, portable quantitative tests for rapid HIV monitoring at the point of care have only recently been introduced to the market. In this review, we discuss low-cost tests for HIV diagnosis and monitoring in low-resource settings, including promising technologies for use at the point of care, that are available or close to market.

Diagnosing acute HIV infection

Individuals with acute HIV infection (AHI) pose a greater transmission risk than most chronically HIV-infected patients and prevention efforts targeting these individuals are important for reducing the spread of HIV infection. Rapid and accurate diagnosis of AHI is crucial. Since symptoms of AHI are nonspecific, its diagnosis requires a high index of suspicion and appropriate HIV laboratory tests. However, even 30 years after the start of the HIV epidemic, laboratory tools remain imperfect and only a few individuals with AHI are identified. We review the clinical presentation of the acute retroviral syndrome, the laboratory markers and their detection methods, and propose an algorithm for the laboratory diagnosis of AHI.

Multinational assessment of blood-borne virus testing and transfusion safety on the African continent

BACKGROUND

Failures of blood screening due to low test quality or poor laboratory technique increase the risk of transfusion-transmitted infections. For this reason, the World Health Organization has recommended a quality control (QC) system for African blood centers.

STUDY DESIGN AND METHODS

We conducted a cross-sectional research assessment of test performance at 51 blood centers in 17 African countries. A blinded, standardized panel containing 25 samples positive for human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) and negative controls was tested by the centers using their operational infectious disease testing consisting of rapid tests, enzyme immunoassays (EIAs), or antigen-antibody EIAs. Nucleic acid testing was not performed.

RESULTS

The overall performances of the 42 assays were the lowest for hepatitis B surface antigen (75.6% sensitivity, 94.5% specificity), then for HCV (80.0% sensitivity, 98.1% specificity) and for HIV (81.4% sensitivity, 99.6% specificity). Poor sensitivity was driven by the use of rapid tests, which had sensitivities of 47.4% for HBV, 63.7% for HCV, and 72.4% for HIV. From a blood screening point of view, 321 (5.6%) infected units would have been transfused due to false-negative results. Assuming that those that were missed by rapid tests (84%) would have been detected by EIAs, 270 viral contaminations (92 HIV, 65 HCV, and 113 HBV) would have been avoided.

CONCLUSION

These results support the discontinuation of rapid tests and implementation of antigen-antibody EIAs whenever possible in Africa. This successful QC program highlights the need for promoting such periodic external quality assessment studies.

Failure of a novel, rapid antigen and antibody combination test to detect antigen-positive HIV infection in African adults with early HIV infection

BACKGROUND

Acute HIV infection (prior to antibody seroconversion) represents a high-risk window for HIV transmission. Development of a test to detect acute infection at the point-of-care is urgent.

METHODS

Volunteers enrolled in a prospective study of HIV incidence in four African cities, Kigali in Rwanda and Ndola, Kitwe and Lusaka in Zambia, were tested regularly for HIV by rapid antibody test and p24 antigen ELISA. Five subgroups of samples were also tested by the Determine Ag/Ab Combo test 1) Antigen positive, antibody negative (acute infection); 2) Antigen positive, antibody positive; 3) Antigen negative, antibody positive; 4) Antigen negative, antibody negative; and 5) Antigen false positive, antibody negative (HIV uninfected). A sixth group included serial dilutions from a p24 antigen-positive control sample. Combo test results were reported as antigen positive, antibody positive, or both.

RESULTS

Of 34 group 1 samples with VL between 5x105 and >1.5x107 copies/mL (median 3.5x106), 1 (2.9%) was detected by the Combo antigen component, 7 (20.6%) others were positive by the Combo antibody component. No group 2 samples were antigen positive by the Combo test (0/18). Sensitivity of the Combo antigen test was therefore 1.9% (1/52, 95% CI 0.0, 9.9). One false positive Combo antibody result (1/30, 3.3%) was observed in group 4. No false-positive Combo antigen results were observed. The Combo antigen test was positive in group 6 at concentrations of 80 pg/mL, faintly positive at 40 and 20 pg/mL, and negative thereafter. The p24 ELISA antigen test remained positive at 5 pg/mL.

CONCLUSIONS

Although the antibody component of the Combo test detected antibodies to HIV earlier than the comparison antibody tests used, less than 2% of the cases of antigen-positive HIV infection were detected by the Combo antigen component. The development of a rapid point-of-care test to diagnose acute HIV infection remains an urgent goal.

Testing for acute HIV infection: implications for treatment as prevention

PURPOSE OF REVIEW

The aim of this study is to give an overview of the recent literature related to HIV testing with an emphasis on detecting acute HIV infection. Testing technology as well as implications for treatment as prevention will be discussed.

RECENT FINDINGS

HIV testing technology continues to evolve. Advances include updated immunologic formats that detect both HIV antibody and antigen (4th generation assays), new nucleic acid amplification tests, and continued development of rapid assays that can be used in either clinical or nonclinical settings. Because of these advances there are proposed changes for HIV diagnostic algorithms to encourage detection of acute infection. These technologic advances have implications for HIV prevention as testing is a cornerstone for all HIV prevention strategies. There is considerable new research indicating that treatment may be an important aspect of HIV prevention. Data also suggest that detection of acute infection will be important for the success of these prevention strategies.

SUMMARY

Continued improvements in technology and testing practice are vital for the success of HIV prevention. Detection of acute or early HIV infection will likely play a key role in the success of treatment as prevention, as well as play an important role in ongoing behavioral prevention strategies.

Identifying HIV infection in South African women: How does a fourth generation HIV rapid test perform?

Background

HIV rapid tests (RT) play an important role in tackling the HIV pandemic in South Africa. Third generation RT that detect HIV antibodies are currently used to diagnose HIV infection at the point of care. Determine Combo (DC) is the first fourth generation RT that detects both p24 antigen (p24Ag) and HIV antibodies (Ab), theoretically reducing the window period and increasing detection rates. Early detection of maternal HIV infection is important to mitigate the high risk of vertical transmission associated with acute maternal infection.

Objectives

We assessed the performance of the DC RT against third generation RT in antenatal and post-partum women.

Methods

Third generation RT Advance Quality and Acon were used in a serial algorithm to diagnose HIV infection in antenatal and post-partum women over six months at a tertiary hospital in Johannesburg, South Africa. This data provided the reference against which the DC RT was compared on plasma and whole blood samples.

Results

The 1019 participants comprised 345 (34%) antenatal and 674 (66%) post-partum women. Ninety women (8.8%) tested HIV-positive of whom 59 (66%) were tested antenatally, and 31 (34%) post-partum yielding prevalence rates of 17.1% and 4.6% respectively. The sensitivity and specificity of the Ab component of DC on plasma antenatally was 100% (93.8% – 100%) and 100% (98.6% – 100%) respectively and post-partum was 100% (88.9% – 100%) and 99.6% (98.8% – 99.9%) respectively. One false positive and not a single true positive p24Ag was detected. Of 505 post-partum women who tested HIV-negative 6–12 months prior to enrolment, 12 (2.4%) seroconverted.

Conclusion

The fourth generation DC offered no advantage over current third generation RT in the diagnosis of HIV infection.

Programmatic evaluation of a combined antigen and antibody test for rapid HIV diagnosis in a community and sexual health clinic screening programme

Background

A substantial proportion of HIV-infected individuals in the UK are unaware of their status and late presentations continue, especially in low prevalence areas. Fourth generation antigen/antibody rapid test kits could facilitate earlier diagnosis of HIV in non-clinical settings but lack data on performance under programmatic conditions.

Methods and Findings

We evaluated the performance of Determine HIV-1/2 Ag/Ab Combo Test (Determine Combo), a rapid test with indicators for both HIV antibodies and p24 antigen, in participants recruited from community outreach and hospital-based sexual health clinics. HIV infection was confirmed using laboratory enzyme-linked immunosorbent assay (EIA), Line Immuno Assay (LIA) and quantitative polymerase chain reaction (PCR). In total, 953 people underwent HIV testing. HIV antibody (Ab) prevalence was 1.8% (17/953). Four false positive rapid tests were identified: two antibody and two p24 antigen (Ag) reactions. Of participants diagnosed as HIV Ab positive, 2/17 (12%) were recent seroconverters based on clinical history and HIV antibody avidity test results. However, none of these were detected by the p24 antigen component of the rapid test kit. There were no other true positive p24 Ag tests.

Conclusion

These data lend support to an increasing body of evidence suggesting that 4th generation rapid HIV tests have little additional benefit over 3rd generation HIV kits for routine screening in low prevalence settings and have high rates of false positives. In order to optimally combine community-based case-finding among hard-to-reach groups with reliable and early diagnosis 3rd generation kits should be primarily used with laboratory testing of individuals thought to be at risk of acute HIV infection. A more reliable point of care diagnostic is required for the accurate detection of acute HIV infection under programmatic conditions.

Universal testing and treatment as an HIV prevention strategy: research questions and methods

Achieving high coverage of antiretroviral treatment (ART) in resource-poor settings will become increasingly difficult unless HIV incidence can be reduced substantially. Universal voluntary counselling and testing followed by immediate initiation of ART for all those diagnosed HIV-positive (universal testing and treatment, UTT) has the potential to reduce HIV incidence dramatically but would be very challenging and costly to deliver in the short term. Early modelling work in this field has been criticised for making unduly optimistic assumptions about the uptake and coverage of interventions. In future work, it is important that model parameters are realistic and based where possible on empirical data. Rigorous research evidence is needed before the UTT approach could be considered for wide-scale implementation. This paper reviews the main areas that need to be explored. We consider in turn research questions related to the provision of services for universal testing, services for immediate treatment of HIV-positives and the population-level impact of UTT, and the research methods that could be used to address these questions. Ideally, initial feasibility studies should be carried out to investigate the acceptability, feasibility and uptake of UTT services. If these studies produce promising results, there would be a strong case for a cluster-randomised trial to measure the impact of a UTT intervention on HIV incidence, and we consider the main design features of such a trial.

Indeterminate and discrepant rapid HIV test results in couples' HIV testing and counselling centres in Africa

Background

Many HIV voluntary testing and counselling centres in Africa use rapid antibody tests, in parallel or in sequence, to establish same-day HIV status. The interpretation of indeterminate or discrepant results between different rapid tests on one sample poses a challenge. We investigated the use of an algorithm using three serial rapid HIV tests in cohabiting couples to resolve unclear serostatuses.

Methods

Heterosexual couples visited the Rwanda Zambia HIV Research Group testing centres in Kigali, Rwanda, and Lusaka, Zambia, to assess HIV infection status. Individuals with unclear HIV rapid antibody test results (indeterminate) or discrepant results were asked to return for repeat testing to resolve HIV status. If either partner of a couple tested positive or indeterminate with the screening test, both partners were tested with a confirmatory test. Individuals with indeterminate or discrepant results were further tested with a tie-breaker and monthly retesting. HIV-RNA viral load was determined when HIV status was not resolved by follow-up rapid testing. Individuals were classified based on two of three initial tests as "Positive", "Negative" or "Other". Follow-up testing and/or HIV-RNA viral load testing determined them as "Infected", "Uninfected" or "Unresolved".

Results

Of 45,820 individuals tested as couples, 2.3% (4.1% of couples) had at least one discrepant or indeterminate rapid result. A total of 65% of those individuals had follow-up testing and of those individuals initially classified as "Negative" by three initial rapid tests, less than 1% were resolved as "Infected". In contrast, of those individuals with at least one discrepant or indeterminate result who were initially classified as "Positive", only 46% were resolved as "Infected", while the remainder was resolved as "Uninfected" (46%) or "Unresolved" (8%). A positive HIV serostatus of one of the partners was a strong predictor of infection in the other partner as 48% of individuals who resolved as "Infected" had an HIV-infected spouse.

Conclusions

In more than 45,000 individuals counselled and tested as couples, only 5% of individuals with indeterminate or discrepant rapid HIV test results were HIV infected. This represented only 0.1% of all individuals tested. Thus, algorithms using screening, confirmatory and tie-breaker rapid tests are reliable with two of three tests negative, but not when two of three tests are positive. False positive antibody tests may persist. HIV-positive partner serostatus should prompt repeat testing.