Detection Of P24 Antigen Research Articles

Fourth-Generation HIV Rapid Tests: Enhanced Sensitivity and Reduced Diagnostic Window for HIV-1 Primary Infection Screening.

As most HIV rapid tests (HRT) detect only HIV-1/2 antibodies, their performance during primary HIV infection is poor. Determine HIV Early detect (Abbott) (Determine) is the only HRT with an HIV-1 p24-antigen detection, but the impact of this addition in shortening the diagnostic window remains unclear. A total of 183 HIV-1 primary infection samples were tested using the HRTs Determine and ONE STEP anti-HIV (1&2) Test (InTec Products) (One-Step). The pre-seroconversion subgroup was defined as p24-antigen positivity without Western blot nor Liaison XL (fouth generation enzyme immunoassay with distinct signal for p24-antigen and HIV-1 antibody) HIV-1 antibodies. Global sensitivity (95% CI) was 95% (91-97) for Determine versus 80% (74%-85%) for One-Step (difference p = 1.38e-06). Pre-seroconversion subgroup sensitivity was lower, at 71.9 (54.6%-84.4%) for Determine and 9.7% (3.3%-24.9%) for One-Step. Among the 45 samples with an HIV-1 infection date, no HRT was reactive up to 2 weeks. Between 2 and 3 weeks, Determine sensitivity was 78% (45%-95%) versus 56% (27%-81%) for One-Step. From 3 weeks to 1 month Determine sensitivity was 90% (62%-98%) and One-Step 45% (21%-72%). The last negative sample occurred at 3 weeks for Determine versus 70-90 days for One-Step. HRT with p24-antigen detection significantly shortens the diagnostic window from approximatively 3 months to 1 month. HRTs should be used with caution in the first month after HIV infection.

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

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

Performance evaluation of the new Access HIV Ag/Ab combo assay on the DxI 9000 Access Immunoassay Analyzer

Fourth-generation HIV immunoassays have been developed to reduce the window period of detection during seroconversion period, allowing for the detection of early and established infections. The aim of this work was to evaluate a newly developed assay, Access HIV Ag/Ab combo on the novel high throughput DxI 9000 Access Immunoassay Analyzer (Beckman Coulter, Inc.). The assay allows for simultaneous qualitative detection and differentiation of HIV-1 p24 antigen and HIV-1/2 antibodies.Assay performance was compared to two gold standard assays, the Abbott Architect HIV Ag/Ab Combo and Roche Elecsys HIV Duo, and assessed in a multicenter study, using a wide panel of samples (n > 9000, clinical samples and viral lysates) representative of genetic diversity for both antibodies and antigens, early phases of infection, negative, and cross-reacting samples.The clinical sensitivity was 100 % for clinical samples as well as for viral lysates. Data on viral lysates and early detection on seroconversion panels showed a better result with the Access assay. Analytical sensitivity showed a limit of p24 detection determined around 0.2 IU/mL. The overall specificity was 99.91 %, and no interference was found using the potentially cross-reactive samples.In conclusion, the Access HIV Ag/Ab combo assay demonstrated its ability for accurate diagnosis of chronic as well as primary HIV infections on the DxI 9000 Analyzer, despite the high level of genetic diversity of these viruses.

Sensitivity and specificity of the new Bio-Rad HIV screening test, Access HIV combo V2.

Bio-Rad is one of the leading human immunodeficiency virus (HIV) screening test manufacturers. This laboratory released in 2021 their new version of the Access combo HIV test. However, to date, there have been no studies regarding its performance, especially its limit of detection of the diverse p24 antigen. We present the sensitivity (chronic and primary HIV-1 infection and HIV-2 chronic infection), specificity (blood donors and hospitalized patients), and raw data for the p24/seroconversion panels the manufacturer gave to the European agencies.

Combining Bioorthogonal Chemistry with Fluorescent Silica Nanoparticles for the Ultrasensitive Detection of the HIV-1 p24 Antigen.

Early detection and viral concentration monitoring of human immunodeficiency virus in resource-poor settings are important to control disease spread and reduce mortality. Nucleic acid amplification tests are expensive for low-resource settings. Lateral flow antibody tests are not sensitive if testing is performed within 7-10 days, and these tests are not quantitative. We describe a signal enhancement technique based on fluorescent silica nanoparticles and bioorthogonal chemistries for the femtomolar detection of the HIV-1 p24 antigen. We developed a magnetic bead-based assay, wherein we used fluorescent-dye-encapsulated silica nanoparticles as reporters. The number of reporters was increased by using bioorthogonal chemistry to provide signal enhancement. The limit and range of detection of the sandwich immunoassay using alternating multiple layers for p24 in human serum were found to be 46 fg/mL (1.84 fM) and 46 fg/mL to 10 ng/mL, respectively. This simple assay was 217-fold higher in sensitivity compared to that of commercial enzyme-linked immunoassays (limit of detection of 10 pg/mL).

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

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. 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). 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%. 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.

Prevalence of HIV P24 Antigen; A Sensitive Marker among Seronegative Antibody Blood Donors in Some Hospitals Within Kaduna Metropolis, Nigeria

Detecting and monitoring HIV infection is crucial for effective disease management. The p24 antigen serves as an early viral marker in HIV diagnosis. Despite advancements in diagnosis and monitoring, there is a need for a comprehensive assessment of p24 antigen prevalence in HIV cases. Therefore, this study aims to ascertain the prevalence of p24 antigen among a diverse population of blood donors in Kaduna metropolis. The study recruited 261 blood donors aged between 18 and 55 from various blood bank units in the metropolis. Initial HIV status determination utilized the Immune-Chromatographic Determine® HIV rapid test kit, followed by re-screening with UnigoldRecombigen HIV 1 and 2, boasting 99.70% specificity and 100% sensitivity. HIGHTOP (HIV) ELISA test kit was employed to screen HIV antibodynegative blood donors for HIV p24 antigen. Additionally, demographic factors like gender, residency, age, and marital status were taken into account. Results indicated p24 antigen detection in 9 out of 261 blood samples, yielding a prevalence of 3.5%. Conversely, 252 samples tested negative for the antigen, resulting in a prevalence of 96.5%. The study's findings support the assertion that HIV p24 antigen serves as a sensitive marker, advocating for its integration into routine blood donor screening within Kaduna metropolis to enhance HIV infection detection rates.

Sensitivity Equalization and Dynamic Range Expansion with Multiple Optofluidic Microbubble Resonator Sensors.

A novel multi-optofluidic microbubble resonator (OMBR) sensitivity equalization method is presented that equalizes the sensing signal from different OMBRs. The method relies on the fact that the ratio of the wavelength shifts to the bulk refractive index sensitivity (BRIS) does not depend on the physical dimensions of the OMBR. The proof of concept is experimentally validated and the sensing signals from individual OMBRs can be directly compared. Furthermore, a wide dynamic range of sensing with favorable consistency and repeatability is achieved by piecing together signals from 20 OMBRs for HIV-1 p24 antigen detection from 50 fg/mL to 100 ng/mL (2.1 fM to 4.2 nM), indicating significant potential for practical applications, such as in drug screening and disease diagnosis.

A microfluidics chemiluminescence immunosensor based on orientation of antibody for HIV-1 p24 antigen detection

The HIV-1 capsid protein, p24 antigen, is a recognizable early diagnostic biomarker for human immune deficiency virus (HIV) infection. However, the existing methods address the limitations of high cost, cumbersome operations, long analysis time, and insufficient sensitivity and selectivity. Herein, an antibody oriented microfluidic chemiluminescence biosensor based on multiple signal amplification strategy was developed for rapid and ultrasensitive detection of HIV-1 p24 antigen. The microfluidic device contained an upstream snake-shape mixing channel and a downstream ship-shape microcavity with micropillar arrays for sufficient mixing of CL reagents, efficient capture of p24 antigen, double antibody sandwich reaction, hybridization chain reaction (HCR) amplification and CL detection. The multiple signal amplification was realized by antibody orientation, multiple HCRs on antibody and initiator chain modified gold nanoparticles (Ab2-AuNPs-I), and HRP and AuNPs synergistic catalyzed CL reaction. Using the platform, the detection of target p24 is converted to the detection of nucleic acid with a limit detection of 0.212 pg mL−1 and excellent specificity within 2 h of total analysis time, which is better or comparable to previously reported biosensors. Moreover, the biosensor exhibited an excellent recovery rate ranging from 92.7% to 102.3%. Therefore, the proposed method holds great potential in clinical diagnosis.

Economics of point-of-care infant HIV tests

Economics of point-of-care infant HIV tests

Flow-Cytometry Intracellular Detection and Quantification of HIV1 p24 Antigen and Immunocheckpoint Molecules in T Cells among HIV/AIDS Patients.

IntroductionHIV p24 antigen-positive T cells measured by flow cytometry (FCM) correlate directly with HIV viral load, inversely with CD4+ T cells, and decrease with antiretroviral therapy (ART). However, the sensitivity of FCM assays depends on the protocol of intracellular staining. Therefore, this study aimed to evaluate the diagnostic performance of our FCM protocol for detection of HIV p24-positive T cells and measure the level of immunocheckpoint molecules (PD1 and TIM3) in T cells.MethodsThe study was conducted at the University of Leipzig hospital between January 2020 and November 2020. Viremic and ART-suppressed HIV-positive patients and negative controls were included in this study. HIV1 p24 KC57-, p24 28B7-, PD1-, and TIM3-positive CD4 and CD3 T cells were analyzed from whole blood using a BD FACS Canto II flow cytometer equipped with FACSDiva software. HIV1 p24 antigen FCM results were compared with HIV1 RNA viral load results measured by Alinity M assays on the fully automated random-access platform. We analyzed the data using SPSS 20.ResultsThe absolute CD4+ and CD4+:CD8+ T-cells ratio showed a significant inverse correlation with HIV1 viral load. Moreover, the absolute CD4+ T-cells count showed a significant inverse correlation with p24 KC57-positive CD4 T cells. The percentage of p24 KC57, p24 28B7, and double-positive CD4 T cells showed significant correlation with HIV1 viral load. PD1 expressing CD4 T cells were higher in ART-viremic cases than controls, while TIM3-expressing CD4 T cells were lower in ART-viremic cases than controls. Sensitivity, specificity, PPV, and NPV of p24 KC57-positive CD4 T cells were 64%, 82%, 78%, and 69%, respectively, for the diagnosis of HIV infection and 55%, 73%, 40%, and 83%, respectively, for treatment monitoring.ConclusionOur protocol showed moderate performance for the diagnosis of HIV infection and treatment monitoring. Therefore, the p24 KC57 but not the p24 28B7 clone could be considered as a simple alternative method for rapid diagnosis of HIV infections and treatment monitoring, particularly in low- and middle-income countries.

Characteristics of recent HIV infection among individuals newly diagnosed as HIV-positive in South Korea (2008–2015)

Most HIV-positive individuals diagnosed in Korea are infected through sexual contact, with the time of HIV infection therefore often being unknown. The aim of this study was to investigate the characteristics of diagnosed patients near the time of HIV seroconversion to establish useful HIV intervention strategies. Cross-sectional study. Newly diagnosed HIV cases based on the national HIV surveillance system in South Korea, 2008–2015. To distinguish recent from long-standing HIV infection among 5898 nationwide HIV-positive specimens, limiting antigen avidity assays (Sedia HIV-1 LAg-Avidity EIA, cut-off = 1.5) were performed. Data on CD4+ T cell count at HIV diagnosis and death from AIDS within one year after first HIV diagnosis were used to distinguish recent HIV infections. Acute HIV infection is characterized by detectable HIV RNA or HIV p24 antigen levels, along with a negative or indeterminate antibody western blot result, but with the subject subsequently testing positive after a predetermined period. We analyzed the characteristics of recent and acute HIV infections by sex, age, nationality, HIV testing site, region, and reason for HIV testing. Recent and acute HIV infections were described as the proportion of recent and acute HIV infections among newly-diagnosed cases in a given year. Recent and acute HIV infections over the 8-year study period were 20.5% (1210/5898) and 9.5% (562/5898), respectively. Both infections were generally higher in the following groups: males, younger age, Koreans, individuals who were tested due to disease, residents of smaller city or rural area, and individuals diagnosed in recent calendar years. Acute infections were significantly higher among individuals tested in hospitals and due to suspected HIV infection. The recent and acute HIV infection in younger age groups (< 30 years) has been increasing in a given year. There was an increase in the proportion of young individuals with recent HIV infection, and we identified risk groups more at risk of HIV infection recently in Korea. Therefore, our results could prove useful for the development and assessment of national HIV prevention strategies in Korea and provide valuable data for further HIV research.

Gingival tissue as a reservoir for human immunodeficiency virus type 1: Preliminary results of a cross-sectional observational study.

Despite combined antiretroviral therapy (cART), total cure of immunodeficiency virus type 1 (HIV-1) infection remains elusive. Chronic periodontitis (CP) is strongly associated with HIV-1 infection. This condition is characterized by an intense inflammatory infiltrate mainly constituted of immune cells which in turn may be a valuable source of HIV-1 reactivation. This study aimed to determine if gingival tissue could act as a reservoir for HIV-1. Twelve patients with HIV-1 and CP and 12 controls (no HIV-1-infection and no CP) were evaluated in a cross-sectional study. RNA viral load and interleukin (IL) levels were determined in blood plasma and saliva. Histological sections of gingival tissue were stained with fluorescent antibodies against p24 antigen and different cellular biomarkers. In six of the 12 patients, HIV RNA load was detected, despite cART; in three of them, expression of viral RNA was also detected in saliva. The levels of IL-2, IL-6, and IL-12 were higher in blood and saliva of patients with HIVand CP than controls. HIV-1 p24 antigen was detected by immunostaining in gingival biopsies of 10 of the 12 patients but in no controls. Immune markers for T cells and antigen-presenting cells were also identified in most patients and some controls. These preliminary data showing the detection of HIV-1 p24 antigen in the gingival biopsies of a significant part of patients with HIV-1 and CP under cART together with the presence of immune cells, plead for the existence of a HIV-1 reservoir in the gingival tissue of this population.

Fluorescence and visual immunoassay of HIV-1 p24 antigen in clinical samples via multiple selective recognitions of CdTe QDs.

Human immunodeficiency virus (HIV) infection inflicts significant economic and social burdens on many countries worldwide. Given the substantial morbidity and mortality from HIV infection, there is an urgent need for accurate and early detection of the virus. In this study, immunofluorescence and visual techniques are describedthat detect the HIV-1 p24 antigen, which relied on selective recognition of Ag+/Ag nanoparticles (Ag NPs) and Cu2+/Cu+ using cadmium telluride quantum dots (CdTe QDs). After the sandwich immunoreactions were accomplished, the alkaline phosphatase (ALP) hydrolyzed L-ascorbic acid 2-phosphate (AAP) to form ascorbic acid (AA) that further reduces Ag+ and Cu2+ to Ag NPs and Cu+, respectively. This method was highly sensitive and selective and could detect as low as 1pg/mL of p24 antigen by naked eyes and had a good linearity in the concentration range 1-100pg/mL. When using Ag+ and Cu2+ as media, the limit of detection (LOD) of the new method was 0.3pg/mL and 0.2pg/mL, respectively. Compared with clinical electrochemiluminescence immunoassay (ECLIA) results and clinical data, this method demonstrated good consistency for the quantification of HIV-1 p24 antigen in 34 clinical serum samples. In addition, this method could accurately distinguish HIV from other viruses and infections such as hepatitis B virus, systemic lupus erythematosus, hepatitis C virus, Epstein-Barr virus, cytomegalovirus, lipemia, and hemolysis. Therefore, our dual-mode analysis method may provide additional solutions to identify clinical HIV infection. An immunofluorescence and visualization dual-mode strategy for the detection of p24 antigen was constructed based on immune recognition reaction and a phenomenon that cadmium telluride quantum dots (CdTe QDs) can selectively recognize Ag+/Ag nanoparticles (Ag NPs) and Cu2+/Cu+.

Use of fourth-generation rapid combined antigen and antibody diagnostic tests for the detection of acute HIV infection in a community centre for men who have sex with men, between 2016 and 2019.

To assess the use of fourth-generation rapid diagnostic tests in identifying acute infection of Human Immunodeficiency Virus (HIV). BCN Checkpoint promotes sexual health among men who have sex with men (MSM), with a focus on diagnosing HIV early, initiating combined antiretroviral treatment (cART) promptly, and recommending regular repeat testing for those who have tested negative. This cross-sectional study included all test results obtained at the centre between 25 March 2016 and 24 March 2019. The Alere™ HIV Combo (now rebranded to Determine™ HIV Ultra, from Abbott) was used to detect p24 antigen (p24 Ag) and/or immunoglobulin M (IgM) and G (IgG) antibodies to HIV-1/HIV-2 (HIV Ab). Rapid polymerase chain reaction (PCR) confirmatory testing and Western blot (WB) were performed for clients with a positive rapid test result. Confirmed HIV cases were promptly referred to the HIV unit for care and cART prescription. A total of 12,961 clients attended BCN Checkpoint during the study and 27,298 rapid tests were performed. 450 tests were found to be reactive, of which 430 confirmed as HIV-positive, representing a prevalence of 3.32%. Four confirmed cases (0.93%) were detected as "p24 Ag only", nine (2.09%) as "both p24 and HIV Ab" and 417 (96.98%) as "HIV Ab only". The "p24 Ag only" group had a 1-log higher viral load than the other groups and initiated treatment on the following working day. Overall, there were 20 false-positive results (0.07% and 4.44% of total and reactive tests, respectively), of which 10 positive for "p24 Ag only" and 10 for "HIV Ab only". Four Acute HIV Infections (AHI), with very high viral loads, have been detected with the "p24 Ag only" while the HIV Ab were still absent. Referral to the HIV unit and initiation of cART on the following working day contributed to improving persons' health and to reduce HIV transmission chain.

Spinal toxoplasmosis in a young man with undiagnosed HIV infection

Spinal cord lesions are potentially devastating conditions leading to reduced mobility, loss of functional independence, and even ventilator dependence, dictated by the level of injury. Tissue diagnosis is paramount to differentiate between primary brain tumours such as ependymomas and glioblastomas, infarction, infection and demyelination. We present the case of a 30-year-old gentleman with subacute neck pain, nausea and evolving right upper limb weakness and paraesthesiae. MRI-spine demonstrated an intramedullary cervical spine mass with associated oedema, thought to represent an ependymoma. Open tissue biopsy revealed numerous bradyzoites on haematoxylin & eosin staining, subsequently confirmed by directed polymerase chain reaction testing as Toxoplasma gondii. Detailed immunological work-up led to a diagnosis of HIV infection, with detection of HIV antibodies and HIV-1 p24 antigen, an HIV-1 viraemia (log 6.33 copies/mL) and low CD4 count (16 cells/mL). Toxoplasmosis is the most common central nervous system infection in HIV patients not receiving appropriate prophylaxis.1 It may occur in up to 30% of such patients who are seropositive for Toxoplasma gondii,2 typically manifesting when CD4+ counts fall below 100 cells/mm3.3 This case highlights the importance of close collaboration between histopathology, microbiology and infectious diseases specialists in diagnosis of a spinal cord infection with associated HIV infection. 1.Porter SB, Sande MA. Toxoplasmosis of the central nervous system in the acquired immunodeficiency syndrome. N Engl J Med 1992; 327: 1643–8.2.Grant IH, Gold JW, Rosenblum M, et al. Toxoplasma gondii serology in HIV-infected patients: the development of central nervous system toxoplasmosis in AIDS. AIDS 1990; 4: 519–21.3.Kaplan JE, Benson C, Holmes KK, et al. Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents. MMWR Recomm Rep 2009; 58: 1–207.

Point-of-care p24 antigen detection for early infant diagnosis of HIV infection: cross-sectional and longitudinal studies in Zambia

BackgroundEarly infant diagnosis of HIV infection is challenging in sub-Saharan Africa, particularly in rural areas, leading to delays in diagnosis and treatment. Use of a point-of-care test would overcome many challenges. This study evaluated the validity of a novel point-of-care p24 antigen detection test (LYNX) in rural and urban settings in southern Zambia.MethodsTwo studies were conducted: a cross-sectional study from 2014 to 2015 at Macha Hospital (LYNX Hospital study) and a longitudinal study from 2016 to 2018 at 12 health facilities in Southern Province, Zambia (NSEBA study). In both studies, children attending the facilities for early infant diagnosis were enrolled and a blood sample was collected for routine testing at the central lab and immediate on-site testing with the LYNX test. The performance of the LYNX test was measured in comparison to nucleic acid-based testing at the central lab.ResultsIn the LYNX Hospital study, 210 tests were performed at a median age of 23.5 weeks (IQR: 8.9, 29.0). The sensitivity and specificity of the test were 70.0 and 100.0%, respectively. In the NSEBA study, 2608 tests were performed, including 1305 at birth and 1222 on children ≥4 weeks of age. For samples tested at birth, sensitivity was 13.6% (95% CI: 2.9, 34.9) and specificity was 99.6% (95% CI: 99.1, 99.9). While specificity was high for all ages, sensitivity increased with age and was higher for participants tested at ≥4 weeks of age (80.6%; 95% CI: 67.4, 93.7). Children with positive nucleic acid tests were more likely to be negative by the LYNX test if their mother received antiretroviral therapy during pregnancy (60.7% vs. 24.2%; p = 004).ConclusionsConsidering the high specificity and moderate sensitivity that increased with age, the LYNX test could be of value for early infant diagnosis for infants ≥4 weeks of age, particularly in rural areas where centralized testing leads to long delays. Point-of-care tests with moderate sensitivity and high specificity that are affordable, easy-to-use, and easily implemented and maintained should be developed to expand access to testing and deliver same-day results to infants in areas where it is not feasible to implement nucleic acid-based point-of-care assays.

Ability of Alere™ HIV Combo to diagnose acute HIV infection is based mainly on HIV-1 p24 antigen detection.

Alere™ HIV Combo is the only rapid and sensitive point-of-care 4th generation (antigen/antibody) HIV test newly available in Thailand which is advantageous of differentiating between positivity of antigen or antibody or both, especially in acute HIV infection (AHI). AHI in this study was defined by positive machine-based 4th generation test with measurable HIV-RNA but negative 3rd generation (IgM/IgG antibody only) tests. To evaluate the performance characteristics of Alere™ HIV Combo. Fifty stored plasma samples of subjects diagnosed with AHI were used to evaluate Alere™ HIV Combo. Of the 50 AHI samples, Alere™ HIV Combo was positive in 37 (74%): 5 with antibody positive only (R1), 26 with p24 antigen positive only (R2), and 6 with both p24 antigen and antibody positive (R3). Mean sample/cut-off (S/ CO) ratios from machine-based 4th generation test of R1, R2 and R3 were 21.55, 148.38 and 72.97 respectively as compared to 7.57 for the 13 non-reactive (NR) samples. The corresponding median log10 HIV-RNA of NR, R1, R2 and R3 were 5.59, 5.86, 7.00 and 6.61 copies/mL respectively. R2 and R3 had significantly higher S/CO and HIV-RNA than NR and R1. Alere™ HIV Combo detected mainly p24 antigen in AHI as seen in 32/50 (64%) subjects and could detect 11/50 (22%) antibody in AHI samples which were missed by the two 3rd generation HIV tests used in our testing algorithm. Alere™ HIV Combo is the ideal screening test in a setting with high AHI where machine-based 4th generation test is not available.

Enhancing the performance of paper-based electrochemical impedance spectroscopy nanobiosensors: An experimental approach

Accurate, rapid, and low-cost molecular diagnostics is essential in managing outbreaks of infectious diseases, such as the pandemic of coronavirus disease 2019 (COVID-19). Accordingly, microfluidic paper-based analytical devices (μPADs) have emerged as promising diagnostic tools. Among the extensive efforts to improve the performance and usability of diagnostic tools, biosensing mechanisms based on electrochemical impedance spectroscopy (EIS) have shown great promise because of their label-free operation and high sensitivity. However, the method to improve EIS biosensing on μPADs is less explored. Here, we present an experimental approach to enhancing the performance of paper-based EIS biosensors featuring zinc oxide nanowires (ZnO NWs) directly grown on working electrodes (WEs). Through a comparison of different EIS settings and an examination of ZnO-NW effects on EIS measurements, we show that ZnO-NW-enhanced WEs function reliably with Faradaic processes utilizing iron-based electron mediators. We calibrate paper-based EIS biosensors with different morphologies of ZnO NWs and achieve a low limit of detection (0.4 pg ml−1) in detecting p24 antigen as a marker for human immunodeficiency virus (HIV). Through microscopic imaging and electrochemical characterization, we reveal that the morphological and the electrochemical surface areas of ZnO-NW-enhanced WEs indicate the sensitivities and sensing ranges of the EIS nanobiosensors. Finally, we report that the EIS nanobiosensors are capable of differentiating the concentrations (blank, 10 ng ml−1, 100 ng ml−1, and 1 μg ml−1) of IgG antibody (CR3022) to SARS-CoV-2 in human serum samples, demonstrating the efficacy of these devices for COVID-19 diagnosis. This work provides a methodology for the rational design of high-performance EIS μPADs and has the potential to facilitate diagnosis in pandemics.

Effect of HIV pre-exposure prophylaxis (PrEP) on detection of early infection and its impact on the appropriate post-PrEP deferral period.

HIV antivirals for pre-exposure prophylaxis (PrEP) are known to affect detection of early HIV infection through suppression of viral load and delayed seroconversion. To cover potential delay in HIV detection associated with PrEP use by blood donors in the context of international reductions in sexual activity-based deferral periods, we analysed the available data to determine the appropriate minimum post-PrEP deferral period for blood donation. Published cases of incident HIV infection when PrEP use was objectively demonstrable were identified, consisting principally of seroconverters from the Partners PrEP study (a clinical trial of PrEP efficacy). Data were reviewed to determine the impact of PrEP on the detection of HIV RNA, p24 Ag and seroconversion delay. Nucleic acid testing (NAT) detected early HIV infection in the presence of PrEP prior to or in concordance with serological testing in approximately 90% of cases. Undetectable HIV RNA would rebound to detectable levels within two months of PrEP cessation. PrEP delayed p24 antigen detection and antibody seroconversion by about 7days. Even when daily PrEP is continued, it is likely that the majority of early HIV infections are detectable by individual donation (ID)-NAT, with p24 Ag or antibody seroconversion occurring conservatively within four weeks of exposure. HIV RNA levels also rebound rapidly in the absence of PrEP. In Australia, a three-month deferral period for blood donation after the last dose of PrEP provides an appropriate safety margin to mitigate the residual risk of transfusion-transmitted HIV.