Reduction of the diagnostic window with a new combined p24 antigen and human immunodeficiency virus antibody screening assay

Real-World Clinical Performance Evaluation of a Fourth-Generation HIV Antigen/Antibody Differentiation Test

BACKGROUND

HIV testing is still an important component of routine sexual health screening, assessment of at-risk individuals and as part of the care of pregnant women. To prevent further transmission of infection, it is important that HIV tests are highly sensitive and that positive cases are not missed. HIV serologic antigen/antibody tests are commonly used as they are capable of detecting recent and established infection.

METHODS

In this study we assessed the performance of the Elecsys HIV Duo assay (Elecsys assay) against the Abbott Architect assay in 10 121 samples from US and non-US adult, pediatric, and pregnant populations including low-risk, high-risk, and known positive cohorts. Congruent repeatedly reactive and/or discrepant samples followed a confirmatory algorithm consisting of an antigen/antibody differentiation assay and a nucleic acid test, as per the study protocol.

RESULTS

The overall sensitivity of the Elecsys assay was 100.00% (95% CI 99.81-100.00 [1977/1977]), and the specificity was 99.84% (95% CI 99.73-99.91 [8129/8142]). The Elecsys assay detected all positive samples within the study, including all 50 antigen-only positive samples and samples from different HIV subtypes, including group O, group M subtypes, HIV-2 positives, and HIV-1 and HIV-2 dual positives.

CONCLUSIONS

The Elecsys HIV Duo assay was highly sensitive for diagnosis of HIV in a range of clinical samples from the United States and outside the United States and is suitable for routine use.

Evaluation of the diagnostic performance and optimal cutoff value of a fourth-generation ELISA, VIDAS HIV-1/2 Duo Ultra assay, in a low-prevalence country

In this study, we described the largest analysis to date conducted with VIDAS® HIV Duo Ultra assay. Additionally, we analyzed the diagnostic performance and cutoff values (TV) of HIV Duo Ultra assay and total cost analysis for HIV testing. Of 11,642 enzyme-linked immunosorbent assay (ELISA)-positive samples referred to our center for confirmation, 2000 were positive with HIV Duo Ultra, and of these, 87% were HIV-1 positive and 0.6% were HIV-1 indeterminate with the confirmatory test. Overall, the false-positivity rate was 1.75% for HIV Duo Ultra assay. The sensitivity and specificity were 100% and 99.1%, respectively, when the TV was set at the recommended cutoff value. Even increasing the cutoff value four times, sensitivity and specificity remained high, pointing out that a TV of 0.99 is highly indicative of HIV positivity. Retesting samples with HIV Duo Ultra assay decreased 80% of the confirmatory tests, revealing a significant decrease of 78% in the total costs and reporting time.

Acute HIV Infection in a Patient with Repeat HIV Antibody/Antigen Negative Results Presenting at an Urban Emergency Department: A Case Report

BACKGROUND

It is not uncommon for patients with human immunodeficiency virus (HIV) infections to visit the emergency department (ED) during seroconversion. However, patients with newly acquired HIV may not have a reactive screening result. We report a case of a patient who initially screened reactive on a fourth generation HIV test and subsequently nonreactive twice, but ultimately had positive viral load tests.

CASE REPORT

A 41-year-old woman experiencing symptoms of a sore throat, odynophagia, and back and flank pain for 5 days presented to the ED. The patient had a reactive HIV screen but negative confirmatory antibody test. The ED provider ordered a HIV viral load, informed the patient, and discharged with oral antibacterial agent. The patient returned the next day and after review of Visit 1 results, the ED provider ordered a second HIV screen, which had a nonreactive result. Another HIV viral load order was placed. The patient was discharged and returned a third time, 4 days after initial presentation. On this visit she was admitted, and the initial HIV viral load result returned positive. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: We report a case of a patient who initially screened reactive on a fourth generation HIV screening and then twice nonreactive on the same screening test, ultimately having positive viral loads. The most probable explanation for her series of atypical HIV results is that the patient presented during the p24 seroconversion window, which is graphically conveyed in Figure 1. If her first screening had been performed during the window, no further test would have been performed to rule out HIV, contributing to misdiagnosis. ED providers need to be aware that, at some time points during seroconversion from "negative" to "positive", patients recently infected with HIV and manifesting prodromal symptoms may nonetheless have a negative screening result.

Developments in the Diagnostic Techniques of Infectious Diseases: Rural and Urban Prospective

Objectives:

Diagnostics is the first step for the treatment and eradication of infectious microbial diseases. Due to ever evolving pathogens and emerging new diseases, there is an urgent need to identify suitable diagnostic techniques for better management of each disease. The success rate of specific diagnostic technique in any population depends on various factors including type of the microbial pathogen, availability of resources, technical expertise, disease severity and degree of epidemic of disease in the area. One of the important tasks of the policy makers is to identify and implement suitable diagnostic techniques for specific regions based on their specific requirements. In this review we have discussed various techniques available in the literature and their suitability for the target population based on above mentioned criteria.

Methods:

Diagnostic techniques evaluation of well documented representative microbial diseases; Tuberculosis (bacterial), Malaria (parasitic) and HIV (viral) were included in the study. Identification and collection of information and data was performed focusing on the diagnostic techniques used from the scientific publications from Pubmed, Science Access, Scopus, EMBASE and several regional databases. WHO and CDC database for Tuberculosis, Malaria and HIV were also included. These techniques were compared with respect to the financial resource availability, expertise and management, functional capacity, pathogen virulence and degree of epidemic in the population.

Results and Conclusion:

In case of Tuberculosis, ELISA and colorimetric techniques are successful in rural and urban communities with 80% – 90% sensitivity. Genotyping and SNP analysis are useful in drug resistant strains. Parasitic disease Malaria also follows the same trend with diagnostic techniques like RDTs being common in both population with fast results and around 90% sensitivity. STD disease like HIV however shows slight different trends due to urgent need of interference in rural epidemics of the disease. Rapid and sensitive immunotechniques like dipsticks and agglutination with almost 100% sensitivity are used in both rural and urban areas. For the confirmation further tests are done like protein Western and NAAT. Advance techniques could be the option for higher epidemic area, drug resistance and disease research, while rapid techniques would be suitable for low income areas and POC facilities. Therefore, suitability of the diagnostic techniques for better management depends not only on the financial resources and assessment skills of a community but sometimes on the disease itself. We have further discussed the technological improvements for specific settings (rural/urban) based on the past research for better management of diseases, which could be implemented for the understanding of understudied and newly emerging diseases.

Misdiagnosis of HIV infection during a South African community-based survey: implications for rapid HIV testing

Introduction: We describe the overall accuracy and performance of a serial rapid HIV testing algorithm used in community-based HIV testing in the context of a population-based household survey conducted in two sub-districts of uMgungundlovu district, KwaZulu-Natal, South Africa, against reference fourth-generation HIV-1/2 antibody and p24 antigen combination immunoassays. We discuss implications of the findings on rapid HIV testing programmes.

Methods: Cross-sectional design: Following enrolment into the survey, questionnaires were administered to eligible and consenting participants in order to obtain demographic and HIV-related data. Peripheral blood samples were collected for HIV-related testing. Participants were offered community-based HIV testing in the home by trained field workers using a serial algorithm with two rapid diagnostic tests (RDTs) in series. In the laboratory, reference HIV testing was conducted using two fourth-generation immunoassays with all positives in the confirmatory test considered true positives. Accuracy, sensitivity, specificity, positive predictive value, negative predictive value and false-positive and false-negative rates were determined.

Results: Of 10,236 individuals enrolled in the survey, 3740 were tested in the home (median age 24 years (interquartile range 19–31 years), 42.1% males and HIV positivity on RDT algorithm 8.0%). From those tested, 3729 (99.7%) had a definitive RDT result as well as a laboratory immunoassay result. The overall accuracy of the RDT when compared to the fourth-generation immunoassays was 98.8% (95% confidence interval (CI) 98.5–99.2). The sensitivity, specificity, positive predictive value and negative predictive value were 91.1% (95% CI 87.5–93.7), 99.9% (95% CI 99.8–100), 99.3% (95% CI 97.4–99.8) and 99.1% (95% CI 98.8–99.4) respectively. The false-positive and false-negative rates were 0.06% (95% CI 0.01–0.24) and 8.9% (95% CI 6.3–12.53). Compared to true positives, false negatives were more likely to be recently infected on limited antigen avidity assay and to report antiretroviral therapy (ART) use.

Conclusions: The overall accuracy of the RDT algorithm was high. However, there were few false positives, and the sensitivity was lower than expected with high false negatives, despite implementation of quality assurance measures. False negatives were associated with recent (early) infection and ART exposure. The RDT algorithm was able to correctly identify the majority of HIV infections in community-based HIV testing. Messaging on the potential for false positives and false negatives should be included in these programmes.

Early Detection of Circulating Antigen and IgM-Associated Immune Complexes during Experimental Mycobacterium bovis Infection in Cattle

The presence of circulating antigen in cattle experimentally infected with Mycobacterium bovis was demonstrated using dual-path platform (DPP) technology. The antigen capture immunoassays employed rabbit polyclonal antibody recognizing predominantly M. tuberculosis complex-specific epitopes and were able to detect soluble substances and whole cells of mycobacteria. The antigen found in serum appeared to be mostly bound to IgM, but not to IgG, within the immune complexes formed at early stages of M. bovis infection. The antigen was also detected in bile and urine, indicating possible clearance pathways. The data correlation analyses supported the idea of the role of IgM responses in antigen persistence during M. bovis infection. The antigen was detectable in serum months prior to detectable antibody seroconversion. This proof-of-concept study suggested the potential for improved immunodiagnostics for bovine tuberculosis.

Bioorthogonal Reaction-Mediated ELISA Using Peroxide Test Strip as Signal Readout for Point-of-Care Testing

This work demonstrates a highly sensitive peroxide test strip (PTS)-based enzyme-linked immunosorbent assay (ELISA) for both qualitative and quantitative detection of drugs of abuse (morphine) and disease biomarkers (interleukin-6 and HIV-1 capsid antigen p24). This color-based PTS is a commercially available product with advantages of low cost, easy operation, and portability, and it is an ideal signal readout strategy in ELISA to simplify the immunoassay procedures and enable point-of-care testing (POCT). In addition, we introduce the bioorthogonal reaction that can effectively amplify the signal by controlling the cycles of bioorthogonal reaction to achieve the desirable sensitivity depending on different analytes. The limit of detection is 0.2 ng/mL for morphine, 3.98 pg/mL for interleukin-6, and 11.6 pg/mL for detection of HIV-capsid antigen (p24). This PTS-ELISA applies to both the qualitative and quantitative detection of IL-6 and p24 in clinical serum samples with good accuracy, which provides a promising tool for the POCT in clinical diagnosis.

Saliva and viral infections

Over the last 10 years there have been only a handful of publications dealing with the oral virome, which is in contrast to the oral microbiome, an area that has seen considerable interest. Here, we survey viral infections in general and then focus on those viruses that are found in and/or are transmitted via the oral cavity; norovirus, rabies, human papillomavirus, Epstein‐Barr virus, herpes simplex viruses, hepatitis C virus, and HIV. Increasingly, viral infections have been diagnosed using an oral sample (e.g. saliva mucosal transudate or an oral swab) instead of blood or urine. The results of two studies using a rapid and semi‐quantitative lateral flow assay format demonstrating the correlation of HIV anti‐IgG/sIgA detection with saliva and serum samples are presented. When immediate detection of infection is important, point‐of‐care devices that obtain a non‐invasive sample from the oral cavity can be used to provide a first line diagnosis to assist in determining appropriate counselling and therapeutic path for an increasing number of diseases.

Current diagnostic methods for HIV

Detection of HIV infection is essential for diagnosis and monitoring of the infection. There are different types of diagnostic tools available that are based on detection of HIV-specific antibodies, viral antigen or nucleic acid. Sensitivities and specificities of assays utilized for HIV detection have improved. Newer HIV testing technologies such as third-generation enzyme immunoassay which detect HIV-specific IgG and IgM antibodies, fourth-generation enzyme immunoassay which detect both anti-HIV antibodies and HIV p24 antigen and nucleic acid based tests for HIV RNA have significantly decreased the window period. This review provides an overview of current technologies for the detection and monitoring of HIV infection and recent advances in the field of HIV diagnosis.

Novel Time-Resolved Fluorescence Europium Nanoparticle Immunoassay for Detection of Human Immunodeficiency Virus-1 Group O Viruses Using Microplate and Microchip Platforms

Accurate detection and quantification of HIV-1 group O viruses have been challenging for currently available HIV assays. We have developed a novel time-resolved fluorescence (TRF) europium nanoparticle immunoassay for HIV-1 group O detection using a conventional microplate enzyme-linked immunosorbent assay (ELISA) and a microchip platform. We screened several antibodies for optimal reactivity with several HIV-1 group O strains and identified antibodies that can detect all the strains of HIV-1 group O that were available for testing. The antibodies were used to develop a conventional ELISA format assay and an in-house developed europium nanoparticle-based assay for sensitivity. The method was evaluated on both microwell plate and microchip platforms. We identified two specific and sensitive antibodies among the six we screened. The antibodies, C65691 and ANT-152, were able to quantify 15 and detect all 17 group O viruses, respectively, as they were broadly cross-reactive with all HIV-1 group O strains and yielded better signals compared with other antibodies. We have developed a sensitive assay that reflects the actual viral load in group O samples by using an appropriate combination of p24 antibodies that enhance group O detection and a highly sensitive TRF-based europium nanoparticle for detection. The combination of ANT-152 and C65690M in the ratio 3:1 was able to give significantly higher signals in our europium-based assay compared with using any single antibody.

Fourth generation assays for HIV testing

INTRODUCTION

Laboratory diagnosis of HIV infection is essential for the prevention of infection and the identification of infected individuals who could benefit from highly active antiretroviral therapy. Since the release of the first assays for the detection of anti-HIV antibodies, the technology of immunoassays has improved.

AREAS COVERED

Fourth generation assays - simultaneously detecting HIV p24 antigen and antibodies - have been developed and have been a major improvement in the detection of HIV infection, with a reduction of the diagnostic window. Studies have provided definite evidence for their clinical utility. Combination assays with separate results for anti-HIV antibodies and p24 antigen have been developed. Expert Commentary: In conclusion, fourth generation assays are an effective tool for the laboratory diagnosis of HIV infection. The ADVIA Centaur HIV Ag/Ab Combo assay is in line with most recent fourth generation assays and its clinical utility has been assessed.

A Novel Electrochemiluminescence Immunosensor for the Analysis of HIV-1 p24 Antigen Based on P-RGO@Au@Ru-SiO₂ Composite

Ru(bpy)3(2+)-doped silica (Ru-SiO2) nanoparticles and gold-nanoparticle-decorated graphene (P-RGO@Au) were combined to form a P-RGO@Au@Ru-SiO2 composite. The composite was used to develop a novel sandwich-type electrochemiluminescence immunosensor for the analysis of HIV-1 p24 antigen. The composite worked as carrier to immobilize target antibody and to build a sandwich-type electrochemiluminescence immunosensor through an interaction between antigen and antibody. Importantly, high ECL signal could be obtained due to the large amounts of Ru(bpy)3(2+) molecules per Ru-SiO2 nanoparticle. The P-RGO@Au composite with good conductivity and high surface area not only accelerated the electron transfer rate but also improved the loading of both ECL molecules and capture antibody, which could further increase the ECL response and result in high sensitivity. Taking advantage of both Ru-SiO2 nanoparticles and the P-RGO@Au composite, the proposed immunosensor exhibited a linear range from 1.0 × 10(-9) to 1.0 × 10(-5) mg mL(-1) with a detection limit of 1.0 × 10(-9) mg mL(-1) for HIV-1 p24 antigen. The proposed ECL immunosensor was used to analyze HIV-1 p24 antigen in human serum, and satisfactory recoveries were obtained, indicating that the proposed method is promising for practical applications in the clinical diagnosis of HIV infection.

Evaluation of performance of human immunodeficiency virus antigen/antibody combination assays in Taiwan

BACKGROUND

The fourth-generation human immunodeficiency virus (HIV) combination assay, which can simultaneously detect the presence of anti-HIV antibody and HIV antigen, has been shown to shorten the window period in HIV diagnosis compared with the third-generation HIV antibody immunoassay. This study was aimed to determine the performance of HIV combination assays in Taiwan, where the HIV-1 seroprevalence is 0.007% and HIV-2 infection has never been reported.

METHODS

Performance of three fourth-generation HIV Ag/Ab combination assays (Dia.Pro, Wantai, and Bio-Rad) and one third-generation HIV Ab immunoassay (AxSYM HIV 1/2 gO) was assessed.

RESULTS

A total of 152 specimens, including 86 confirmed HIV-seropositive and 66 HIV-seronegative samples, were used in the study. The sensitivity of four assays varied from 98.8% to 100%, and specificity varied from 98.5% to 100%. Performance of the 75 equivocal samples, the HIV status of which was confirmed later, in terms of negative prediction varied from 81.8% to 87.5%. The Bio-Rad and Dia.Pro assays exhibited higher sensitivity for the detection of p24 antigen among the three fourth-generation HIV combination assays.

CONCLUSION

The three fourth-generation HIV Ag/Ab combination assays exhibited better sensitivity, specificity, and negative prediction than the third-generation HIV Ab immunoassay.

Evaluation of HIV antigen/antibody combination ELISAs for diagnosis of HIV infection in Dar Es Salaam, Tanzania

INTRODUCTION

The aim of this study was to evaluate the performance of Enzygnost HIV Integral II antigen/antibody combination ELISAs in order to formulate HIV ELISA testing algorithms for the Ministry of Health and Social Welfare, Tanzania.

METHODS

This was a laboratory-based evaluation of Enzygnost HIV Integral II Antibody/ Antigen, Murex HIV antigen/antibody and Vironostika HIV Uniform II antigen/antibody conducted between October 2011 and May 2012.

RESULTS

A total of 600 blood samples were included in the evaluation. A total of 209/596 (35.1%) serum samples were confirmed HIV positive. Of these, the prevalence of HIV infection was 2.3% (3/130), 2.3% (3/127), 2.2% (3/139) and 100% (200/200) for VCT clients, ANC attendees, blood donors and CTC patients, respectively. Three hundred and eighty seven (64.9%) were HIV negative samples. Sensitivity was 100% (95% CI; 98.3-100%) for all the three HIV ELISAs. The specificity for the Enzygnost HIV Integral II and Murex was 100% (95% CI; 99.1-100%). The final specificity at repeat testing was 99.5% (95% CI; 98.2-99.9%) for Vironostika. Enzygnost HIV Integral II detected HIV infection seven days since first bleed.

CONCLUSION

Initial testing using either Vironostika or Murex HIV antigen/antibody combination ELISA followed by testing of reactive samples on the Enzygnost HIV Integral II gave a sensitivity and specificity of 100% with reduced window period. Combination of two HIV antigen/antibody combination ELISAs can be used as an alternative confirmatory testing strategy for screening of donated blood at the National and Zonal blood transfusion centres and in lab diagnosis of HIV infection.

Development of an integrase-based ELISA for specific diagnosis of individuals infected with HIV

Currently, enzyme immunoassays (EIAs) are the most common immunological diagnostic methods that are used as the screening tool in HIV detection. Among all three major genes of HIV, the products of gag and env are usually used in EIAs (ELISAs and rapid tests). Hence, the presence of cross reacting antibodies against these antigens leads to the appearance of repetitive false positive results in screening tests. Re-testing the primary reactive samples with EIAs using other HIV antigens can considerably reduce the rate of false positive results. The products of pol gene may act as an appropriate candidate in this context. Integrase is a conserved and immunogenic product of HIV, encoded by the pol gene. The aim of this research was to determine the sensitivity and specificity of an ELISA detecting integrase antibodies. Recombinant integrase was produced in Escherichia coli to develop the integrase-based ELISA. Assay performance was evaluated by HIV positive and negative sera and an HIV panel of BBI (PRB-601). The sensitivity and specificity of assay was determined as 96.7 [95% confidence interval: 91.3-98.9%] and 100% [95% CI: 96.1-100%], respectively. High specificity of this assay may suggest its possible use in the detection of HIV.

Screening Donated Blood for Transfusion Transmitted Infections by Serology along with NAT and Response Rate to Notification of Reactive Results: An Indian Experience

Background. Transfusion safety begins with healthy donors. A fundamental part of preventing transfusion transmitted infections (TTIs) is to notify and counsel reactive donors. Donor notification and counselling protect the health of the donor and prevent secondary transmission of infectious diseases. Methods. 113,014 donations were screened for TTIs, namely, HIV, HBV, HCV, and syphilis, by serology and nucleic acid testing. All reactive donors were retested (wherever possible) and notified of their status by telephone or letter. All initial reactive screens were followed over six months. Results. We evaluated 2,838 (2.51%) cases with reactive screening test results (1.38% HBV, 0.54% HCV, 0.27% HIV, and 0.32% syphilis). Only 23.3% of donors (662) responded to notification. The response among voluntary donors was better as compared to the replacement donors (43.6% versus 21.2%). Only 373 (56.3%) responsive donors followed their first attendance at referral specialties. Over six months, only 176 of 662 (26.6%) reactive donors received treatment. Conclusion. Our study shed light on the importance of proper donor counselling and notification of TTI status to all reactive donors who opt to receive this information. There is also an urgent need to formulate the nationally acceptable guidelines for notification and follow-up of reactive donors.

Prolonged second diagnostic window for human immunodeficiency virus type 1 in a fourth-generation immunoassay: are alternative testing strategies required?

Diagnosis of acute HIV is done by patient history and examination and testing of RNA, proviral DNA, and serology using fourth-generation antigen/antibody detection assays. We describe an HIV-1 primary infection with a second diagnostic window of 18 to 34 days on a fourth-generation immunoassay, which would have been missed using some current algorithms. Caution must be exercised when fourth-generation HIV-1 immunoassays are interpreted in isolation, and additional testing should be considered depending on patient risk assessment.

Prevalence of p24 antigen among a cohort of HIV antibody negative blood donors in Sokoto, North Western Nigeria--the question of safety of blood transfusion in Nigeria

INTRODUCTION

Blood transfusions remain a substantial source of HIV in SSA particularly among children and pregnant women.

AIMS AND OBJECTIVES

This aim of this retrospective study was to investigate the prevalence of p24 antigen among HIV antibody seronegative blood donors in Sokoto, North West Nigeria.

METHODS

A total of 15,061 HIV antibody negative blood donors with mean age and age range (29.2 ± 8.18 and 18-50 years) were screened for p24 antigen between January 2010 to July 2013 using the Diapro Diagnostic immunoassay kit for P24 antigen (King Hawk Pharmaceuticals Beijing China).

RESULTS

The overall prevalence of p24 antigen among the HIV antibody negative donors sample was 5.84%. The yearly prevalence was 9.79, 8.12, 2.7 and 2.84% respectively in 2010, 2011, 2012 and 2013. Of the total number of blood donor tested, 14,968 (99.38%) were males while 93 (0.62%) were females. The prevalence of P24 antigen was significantly higher among male blood donors 873 (5.8%) compared to females 7(0.05%), (p= 0.001). P24 positivity was significantly higher among blood group O blood donors compared to A, B and AB donors (494 (3.29%) compared to 184 (1.89%), 196 (1.30%) and 6 (0.04%)) respectively, p = 0.001). The prevalence of P24 antigen was significantly higher among Rhesus positive blood donors compared to Rhesus negative (807 (5.36%) versus 73 (0.48%), p =0.001).

CONCLUSION

Blood transfusion in Nigeria is associated with increased risk of HIV transmission. There is the urgent need to optimize the screening of blood donors in Nigeria by the inclusion of p24 antigen testing into the blood donor screening menu. The Nigerian government urgently need to adopt the WHO blood safety strategies to reduce the risk of transmission of HIV through blood transfusion.

Screening of HIV infection: role of molecular and immunological assays

Due to technical improvements and new developments of immunological assays, the reliability of serological laboratory diagnosis of HIV infection has improved considerably and the residual risk, due to the diagnostic window for transfusion-transmitted HIV, has been reduced significantly. Through the addition of nucleic acid amplification tests (NAT) to blood donor screening, the residual risk can de further decreased by up to 50%, depending on the sensitivity of the NAT protocol and whether individual or pooled blood donations are screened. In-house and commercially available NAT have been implemented in blood banks as HIV only or multiplexed HIV and hepatitis B or C virus assays. As an alternative to separate antigen and antibody screening, combined fourth-generation assays have been developed in 1997, and have achieved a high degree of sensitivity and specificity. Thus, they can replace stand-alone antigen and third-generation antibody assays. While they are used in the routine diagnostics of HIV infection in many countries throughout the world, they probably represent no alternative for NAT in blood-donor screening in industrialized countries. In the next few years, technical improvements will further simplify NAT screening. While there is still some potential to improve the detection threshold of NAT, the sensitivity of the antigen module of fourth-generation assays (a lowest concentration of 3-5 pg of p24 antigen) is probably very close to its technical limit.

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%).

Clinical evaluation of BioPlex 2200 HIV Ag-Ab, an automated screening method providing discrete detection of HIV-1 p24 antigen, HIV-1 antibody, and HIV-2 antibody

Early and accurate diagnosis is essential for optimal therapeutic outcomes in patients infected with HIV. Currently, none of the commercially available fourth-generation assays differentiate HIV-1 and HIV-2 antibodies (Ab) or the HIV-1 p24 antigen (Ag). The aim of this study was to evaluate the performance of a novel assay, the BioPlex 2200 HIV Ag-Ab. This assay uses a multiplex flow immunoassay design allowing the simultaneous detection and identification of antibodies to HIV-1 (groups M and O), HIV-2, and the HIV-1 p24 antigen, in addition to providing a traditional composite result. A total of 1,505 routine serum samples were prospectively tested. Results were compared with those from the Architect HIV Combo assay. The sensitivity of the BioPlex 2200 was 100%. The specificity assessed on repeated false-positive samples was 99.5%. In addition, 524 frozen specimens from patients known to be infected with HIV-1 or HIV-2 were tested. Of these specimens, 420 were infected with HIV-1, including 156 of known genotypes, 86 were infected with HIV-2, 7 were infected with HIV-1 and HIV-2, and 11 were from patients with acute HIV infection. Sensitivity was 100% for the HIV genotypes tested. The differentiation capabilities of the BioPlex 2200 HIV Ag-Ab assay for HIV-1, HIV-2, dual HIV-1/HIV-2, and early infections were 100%, 90.7%, 100%, and 90.9%, respectively. The BioPlex 2200 is a sensitive and specific assay that offers advantages over conventional HIV combo assays, also referred to as fourth-generation assays, to accurately differentiate and report HIV-1 p24 antigen and HIV-1 and HIV-2 antibodies.

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.

Detecting viruses by using salivary diagnostics

BACKGROUND

Diagnostics that involve the use of oral fluids have become increasingly available commercially in recent years and are of particular interest because of their relative ease of use, low cost and noninvasive collection of oral fluid for testing.

TYPES OF STUDIES REVIEWED

The authors discuss the use of salivary diagnostics for virus detection with an emphasis on rapid detection of infection by using point-of-care devices. In particular, they review salivary diagnostics for human immunodeficiency virus, hepatitis C virus and human papillomavirus. Oral mucosal transudate contains secretory immunoglobulin (Ig) A, as well as IgM and IgG, which makes it a good source for immunodiagnostic-based devices.

CLINICAL IMPLICATIONS

Because patients often visit a dentist more regularly than they do a physician, there is increased discussion in the dental community regarding the need for practitioners to be aware of salivary diagnostics and to be willing and able to administer these tests to their patients.

Real-life evaluation of a human immunodeficiency virus screening algorithm using a single combined p24 antigen-antibody assay

Since May 2010, human immunodeficiency virus (HIV) screening in France has been performed using a single combined fourth-generation assay. One of our major concerns is to verify that this screening strategy is able to diagnose HIV primary infection as soon as possible. Thus, the sensitivity and specificity of this strategy were evaluated on 49,623 serum samples, including 29 primary infections, received for routine HIV testing between September 2010 and November 2011. Specimens were screened using the Enzygnost HIV Integral II enzyme-linked immunosorbent assay (ELISA) kit. All positive sera, according to the manufacturer's recommendations [signal-to-cutoff ratio (S/CO) ≥  1] were retested using the Architect HIV Ag/Ab Combo. Moreover, we defined a grey zone (0.5 < S/CO < 1) and sera within this grey zone were retested using the VIDAS HIV DUO Ultra test and HIV-1 RNA was checked by the Abbott RealTime PCR kit. Screening tests were positive for all primary infections. All samples within the grey zone proved VIDAS HIV DUO Ultra and HIV-1 RNA negative. Overall, the ELISA test sensitivity and specificity were 100 and 99.79 %, respectively. The false-positive rate was higher when S/CO was in the low range (1 to 5). Adding a second screening test for positive sera reduced the false-positive rate from 0.20 to 0.02 %. HIV screening with a single combined assay did not miss any documented primary infection during this evaluation period, even without extending the positivity zone.

Performance evaluation of a new fourth-generation HIV combination antigen-antibody assay

Education and diagnostic tests capable of early detection represent our most effective means of preventing transmission of human immunodeficiency virus (HIV). The importance of early detection is underlined by studies demonstrating increased life expectancy following early initiation of antiviral treatment. The Elecsys^® HIV combi PT assay is a fourth-generation antigen–antibody combination assay developed to allow earlier detection of seroconversion, and to have increased sensitivity and improved specificity. We aimed to determine how early the assay could detect infection compared with existing assays; whether all HIV variants could be detected; and the assay’s specificity using samples from blood donors, routine specimens, and patients with potential cross-reacting factors. Samples were identified as positive by the Elecsys^® assay 4.9 days after a positive polymerase chain reaction result (as determined by the panel supplier), which was earlier than the 5.3–7.1 days observed with comparators. The analytical sensitivity of the Elecsys^® HIV combi PT assay for the HIV-1 p24 antigen was 1.05 IU/mL, which compares favorably with the comparator assays. In addition, the Elecsys^® assay identified all screened HIV subtypes and displayed greater sensitivity to HIV-2 homologous antigen and antibodies to HIV-1 E and O and HIV-2 than the other assays. Overall, the specificity of the Elecsys^® assay was 99.88 % using samples from blood donors and 99.81 % when analyzing unselected samples. Potential cross-reacting factors did not interfere with assay performance. The Elecsys^® HIV combi PT assay is a sensitive and specific assay that has been granted the CE mark according to Directive 2009/886/EC.

An amperometric immunosensor based on a polyelectrolyte/gold magnetic nanoparticle supramolecular assembly--modified electrode for the determination of HIV p24 in serum

A novel supramolecular amperometric immunosensor for the determination of Human Immunodeficiency Virus antigen p24 (HIV p24) was built up using the electrostatic layer-by-layer self-assembly technique upon a gold electrode with HIV p24 antibody (anti-p24) being immobilized on polyelectrolyte/gold nanoparticle multilayer films. The multilayer films were composed of poly(L-lysine) (pLys) and mercaptosuccinic acid (MSA) stabilized Fe₃O₄(core)/gold(shell) nano particles (GMPs).The immunosensor preparation steps were monitored by X-ray fluorescence spectrometry (XRFS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In pH 6.5 PBS, after the immunosensor was incubated with HIV p24 solution at 25 °C for 5 min, the electron transfer access of FeCN is partially inhibited, which leads to a linear decrease of peak current. In addition, the performance of the immunosensor was studied in detail. It offers high-sensitivity for the detection of p24 and has good correlation for the detection of p24 in the range of 0.1 to 100.0 ng/mL with a detection limit of 0.05 ng/mL estimated at a signal-to-noise ratio of 3. The proposed immunosensor was used to analyze p24 in human serum specimens and the results showed the developed immunosensor provides a promising alternative approach for detecting p24 in the early diagnosis of AIDS patients.

Rapid detection and differentiation of antibodies to HIV-1 and HIV-2 using multivalent antigens and magnetic immunochromatography testing

A simplified lateral-flow assay for the detection of antibodies to HIV using magnetic-bead conjugates and multibranched peptides from both HIV-1 and HIV-2 was developed. Magnetic immunochromatography testing (MICT) uses a standard lateral-flow platform that incorporates magnetic-bead conjugates for quantitative measurement of the magnetic field distortion associated with the bound magnetic conjugate (reported as adjusted relative magnetic units [MAR]). The results of the optimized MICT assay were compared to standard enzyme immunoassay (EIA) and Western blotting (WB) results using a blinded 649-member panel of specimens from the United States, Cameroon, and West Africa. The panel was comprised of samples from individuals infected with various HIV-1 subtypes (n = 234) or HIV-2 (n = 65) and HIV-seronegative specimens (n = 350). Additionally, 13 HIV-1 seroconversion panels (total specimens = 85), a worldwide panel containing seven of the major circulating HIV-1 subtypes (n = 18), an HIV-2 panel, an HIV-1/HIV-2 mixed panel, and 100 prospective specimens were tested with completely concordant results. Assay reproducibility (observed MAR) for both intra- and interrun testing was excellent, with coefficients of variation of <12%. MICT can provide a rapid, low-cost method of determining HIV antibody status requiring no subjective interpretations.

Inaccurate diagnosis of HIV-1 group M and O is a key challenge for ongoing universal access to antiretroviral treatment and HIV prevention in Cameroon

Background

Increased access to HIV testing is essential in working towards universal access to HIV prevention and treatment in resource-limited countries. We here evaluated currently used HIV diagnostic tests and algorithms in Cameroon for their ability to correctly identify HIV infections.

Methods

We estimated sensitivity, specificity, and positive and negative predictive values of 5 rapid/simple tests, of which 3 were used by the national program, and 2 fourth generation ELISAs. The reference panel included 500 locally collected samples; 187 HIV -1 M, 10 HIV-1 O, 259 HIV negative and 44 HIV indeterminate plasmas.

Results

None of the 5 rapid assays and only 1 ELISA reached the current WHO/UNAIDS recommendations on performance of HIV tests of at least 99% sensitivity and 98% specificity. Overall, sensitivities ranged between 94.1% and 100%, while specificities were 88.0% to 98.8%. The combination of all assays generated up to 9% of samples with indeterminate HIV status, because they reacted discordantly with at least one of the different tests. Including HIV indeterminate samples in test efficiency calculations significantly decreased specificities to a range from 77.9% to 98.0%. Finally, two rapid assays failed to detect all HIV-1 group O variants tested, with one rapid test detecting only 2 out of 10 group O specimens.

Conclusion

In the era of ART scaling-up in Africa, significant proportions of false positive but also false negative results are still observed with HIV screening tests commonly used in Africa, resulting in inadequate treatment and prevention strategies. Depending on tests or algorithms used, up to 6% of HIV-1 M and 80% of HIV-1 O infected patients in Cameroon do not receive ART and adequate counseling to prevent further transmission due to low sensitivities. Also, the use of tests with low specificities could imply inclusion of up to 12% HIV negative people in ART programs and increase budgets in addition to inconveniences caused to patients.

The risk of a second diagnostic window with 4th generation HIV assays: Two cases

BACKGROUND

Despite the improved sensitivity of the 4th generation combined antigen/antibody HIV assays, detection of HIV in the early phase of an infection may still be ineffective.

OBJECTIVES

Description of two cases that highlight the existence of the "second diagnostic window phase" observed with commonly used sensitive 4th generation HIV assays.

STUDY DESIGN

Samples were screened with different 4th generation HIV assays. HIV infection was confirmed with an HIV I/II antibody assay, a HIV-1 p24 antigen assay, the INNO-LIA HIV I/II Score Line immunoassay and HIV-1 PCR.

RESULTS

In both investigated cases, the limitations of the 4th generation HIV assays within the second diagnostic window were apparent.

CONCLUSIONS

The overall sensitivity of the commercial 4th generation HIV assays is currently higher than the 3rd generation HIV assays. Nevertheless, the rare occurrence of a second diagnostic window with 4th generation HIV assays strongly suggests that the following up testing algorithms need to be adjusted accordingly.

Performance evaluation of the new fully automated human immunodeficiency virus antigen-antibody combination assay designed for blood screening

BACKGROUND

Before the introduction of human immunodeficiency virus (HIV) combination assays, serologic diagnosis of HIV infection was performed with assays that detected either antibodies or p24 antigen. Owing to the capability to detect the early appearance of p24 antigen, combination assays that are designed for simultaneous detection of antibodies and antigen can significantly reduce the diagnostic window.

STUDY DESIGN AND METHODS

Specificity and sensitivity of a commercially available HIV antigen-antibody combination assay (Abbott PRISM; assay is not licensed by the FDA for use in the United States) were evaluated in a multicenter study by testing volunteer blood donors, hospitalized patients, seroconversion panels, and p24 antigen and HIV antibody subtype panels. Performance data were compared to a commercially available HIV combination assay and the PRISM HIV O Plus assay.

RESULTS

Apparent specificity of 99.95 percent was observed in the donor population for the PRISM HIV antigen-antibody combination assay, and better seroconversion sensitivity was demonstrated compared with another combination assay and the PRISM HIV O Plus assay. Analytical HIV antigen detection sensitivity averaged 33 pg per mL on the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSAPS) panel. Furthermore, comparable antigen sensitivity was demonstrated for 32 HIV-1 group M subtype and group O panels. The PRISM HIV combination assay detected all HIV-1 group M and O and HIV-2 antibody-positive specimens evaluated.

CONCLUSIONS

The PRISM HIV antigen-antibody combination assay demonstrated a significant reduction of the window period for diagnosis of HIV infection. The assay demonstrated enhanced specificity and sensitivity along with broad subtype detection. The assay performance represents the "state-of-the art" technology for serologic blood screening of HIV infection.

Evaluation of the Murex HIV Ag/Ab Combination assay when used with dried blood spots

This study evaluated the ability of the Murex HIV Ag/Ab Combination assay to detect human immunodeficiency virus (HIV) antibodies in 12 617 dried blood spots (DBSs) on filter paper. The assay had an overall sensitivity of 99.6% and a specificity of 99.9%. In view of its ability to detect p24 antigen and both HIV-1 and HIV-2 antibodies in samples collected in the form of DBSs, the Murex Ag/Ab Combination assay is suitable for use as a standard screening assay for seroprevalence studies, as well as for routine diagnostic use in clinical laboratories.

Could the new HIV combined p24 antigen and antibody assays replace p24 antigen specific assays?

The performance of twelve HIV combined p24 antigen and antibody assays available in Europe were compared. The assays were examined with a total of 1983 samples that included 1005 unselected HIV negative samples, 7 HIV-1 p24 Ag reference samples with HIV-1 Ag, 10 samples of a HIV antigen sensitivity commercial panel, 124 samples of 31 p24 antigen panels of different HIV-1 subtypes, 168 members of 24 HIV-1 seroconversion panels, 559 HIV-1 (groups M and O) antibody positive samples and 110 HIV-2 antibody positive samples. The specificity ranged from 99.4 to 100%. Ten of the 12 assays detected all anti-HIV positive samples irrespective of genotype while two assays missed one sample each (one subtype F and one subtype C). The combined assays could be classified into three groups. The first includes two assays (Enzygnost HIV Integral and Vironostika Ag/Ab) that have a clinical sensitivity similar to the two antibody only assays. The second includes the seven assays that detected infection after the p24 antigen only assay and show a delay from 3.3 to 5.17 days after HIV-1 RNA. The third group detected the infection before the p24 antigen assay and less than 3 days after nucleic acid testing (NAT). The improved ability to detect p24 Ag, at levels similar to specific HIV Ag assays, suggests that these new HIV combined Ag/Ab assays could replace p24 antigen only assays in situations for blood or organ screening when NAT is not feasible or not affordable.

Early identification of seronegative human immunodeficiency virus type 1 infection with severe presentation

Specific antibodies against human immunodeficiency virus (HIV), usually used for diagnosis, almost invariably become detectable within 3 months of exposure. We report on a patient whose HIV infection was identified early by a combined antigen/antibody test, but seroconversion did not occur for 7 months, until the implementation of antiretroviral therapy.

Optimized virus disruption improves detection of HIV-1 p24 in particles and uncovers a p24 reactivity in patients with undetectable HIV-1 RNA under long-term HAART

HIV-1 p24 antigen (p24) measurement by signal amplification-boosted ELISA of heat-denatured plasma is being evaluated as an alternative to HIV-1 RNA quantitation in resource-poor settings. Some observations suggested that virion-associated p24 is suboptimally detected using Triton X-100-based virus dissociation buffer (kit buffer). A new reagent (SNCR buffer) containing both denaturing and non-denaturing detergents was therefore developed and evaluated. The SNCR buffer increased the measured p24 concentration about 1.5- to 3-fold in HIV-negative plasma reconstituted with purified HIV-1 particles, while not increasing the background. Among 127 samples of HIV-1-positive patients with moderate to high concentrations of HIV-1 RNA the increase was about threefold across the entire concentration range (P < 0.0001). Specificity before neutralization among prospectively tested clinical samples ruled HIV-negative was 828 of 845 (98.0%) for the SNCR buffer and 464 of 479 (96.9%) for kit buffer. Specificity after confirmatory neutralization of reactive samples or a follow-up test was 100% with either buffer. Surprisingly, the SNCR buffer revealed a p24 reactivity in 115 of 187 samples (61.5%) from adult patients exhibiting undetectable HIV-1 RNA below 5 copies/ml for a duration of 6-30 months under HAART (3.7% with kit buffer). The rate of p24 reactivity in these patients did not decrease with duration of HAART. In conclusion, the SNCR buffer improves the detection of particle-associated HIV-1 p24, thereby increasing the measured p24 concentration in samples with medium to high HIV-1 RNA. It also uncovers the presence of a p24 reactivity, whose identity remains to be determined, in a significant fraction of samples with undetectable HIV-1 RNA under long-term HAART.

Evaluation of HIV antibody and antigen/antibody combination ELISAs for use in an alternative confirmatory HIV testing strategy in Dar es Salaam, Tanzania

The aim of this study was to evaluate the performance of two antibody enzyme-linked immunosorbent assays (ELISAs) [Vironostika Uni-Form II plus O and Enzygnost anti-HIV-1/2 Plus], and two antigen/antibody combination ELISAs [Murex and Vironostika HIV Uni-Form II] for use in an alternative confirmatory HIV diagnostic testing strategy in Dar es Salaam, Tanzania. Altogether, 1380 serum samples were included. All ELISA reactive samples were tested using the Inno-Lia antibody assay and discrepant samples were tested on the Innotest p24 antigen assay. Three hundred and one (21.8%) samples were confirmed HIV-1 antibody positive by Inno-Lia including 27/508 (5.3%) from blood donors, 65/511 (12.7%) from pregnant women and 209/361 (57.9%) from hospital patients. The sensitivity at initial testing was 100% (95% CI; 98.8-100%) for all assays except Vironostika Uni-Form II plus O (99.7%; 95% CI; 98.2-99.9%) which showed one false negative sample at initial testing but 100% sensitivity after repeat testing. The final specificity at repeat testing was 100% (95% CI; 99.7-100%) for Enzygnost anti-HIV-1/2 Plus, 99.4% (95% CI; 98.8-99.8%) for each of the antigen/antibody combination ELISAs and 97.9% (95% CI; 96.8-98.6%) for Vironostika plus O ELISA. An alternative confirmatory HIV testing strategy based on initial testing on any of the two antigen/antibody assays followed by testing of reactive samples on the Enzygnost anti-HIV-1/2 Plus assay gave 100% specificity (95% CI; 99.7-100%).

Comparative evaluation of TRI-DOT Rapid HIV test with fourth-generation ELISA for the detection of human immunodeficiency virus

This study evaluated the TRI-DOT Rapid HIV test for the early detection of human immunodeficiency virus (HIV) infection in comparison with a fourth-generation ELISA (Vironostika HIV Uniform II). Of 23,609 sera, seven (0.03%) gave discordant results. Six of these were reactive only by the fourth-generation assay and were p24 antigen-positive by VIDAS DUO, Western blot and qualitative RT-PCR tests. The remaining discordant serum was considered to be false-positive by the TRI-DOT assay, as it was negative by repeat ELISA and Western blot tests. The sensitivity and specificity of the TRI-DOT test were 99.48% and 99.99%, respectively, compared with the fourth-generation ELISA.