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

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

Comparative evaluation of the VIDAS HIV DUO Ultra assay for combined detection of HIV-1 antigen and antibodies to HIV

The aim of the study was to evaluate the performance of the combined antigen and antibody HIV screening assay VIDAS HIV DUO Ultra (BioMérieux, Marcy l'Etoile, France) in comparison with two other combined tests: the former version of the same test (VIDAS HIV DUO, BioMérieux) and the AxSYM HIV Ag/Ab Combo assay (Abbott Laboratories, Rungis, France). A prospective study was performed on serum specimens received on a routine basis for HIV testing: 1443 blood samples were tested with the three assays. Sensitivity was 100% for the three tests. Specificity assessed on repeated false-positive samples was 99.86, 99.03 and 99.65% for VIDAS HIV DUO Ultra, VIDAS HIV DUO and AxSYM HIV Ag/Ab Combo, respectively. In addition, 14 seroconversion panels were tested with the VIDAS DUO Ultra and AxSYM HIV Ag/Ab Combo assays. For four of these panels, a positive signal was detected one blood sampling point earlier with the VIDAS DUO Ultra assay, corresponding to a higher sensitivity of the HIV antigen test. These results indicate that the VIDAS HIV DUO Ultra exhibits an improved specificity with comparison to the former version of this assay and an excellent sensitivity for early detection of HIV seroconversion.     

Performance comparison of the 4th generation Bio-Rad Laboratories GS HIV Combo Ag/Ab EIA on the EVOLIS™ automated system versus Abbott ARCHITECT HIV Ag/Ab Combo,Ortho Anti-HIV 1 + 2 EIA on Vitros ECi and Siemens HIV-1/O/2 enhanced on Advia Centaur

BackgroundA multisite study was conducted to evaluate the performance of the Bio-Rad 4th generation GS HIV Combo Ag/Ab EIA versus Abbott 4th generation ARCHITECT HIV Ag/Ab Combo. The performance of two 3rd generation EIAs, Ortho Diagnostics Anti-HIV 1 + 2 EIA and Siemens HIV 1/O/2 was also evaluated.ObjectiveStudy objective was comparison of analytical HIV-1 p24 antigen detection, sensitivity in HIV-1 seroconversion panels, specificity in blood donors and two HIV false reactive panels.Study designAnalytical sensitivity was evaluated with International HIV-1 p24 antigen standards, the AFFSAPS (pg/mL) and WHO 90/636 (IU/mL) standards; sensitivity in acute infection was compared on 55 seroconversion samples, and specificity was evaluated on 1000 negative blood donors and two false reactive panels.ResultsGS HIV Combo Ag/Ab demonstrated better analytical HIV antigen sensitivity compared to ARCHITECT HIV Ag/Ab Combo: 0.41 IU/mL versus 1.2 IU/mL (WHO) and 12.7 pg/mL versus 20.1 pg/mL (AFSSAPS); GS HIV Combo Ag/Ab EIA also demonstrated slightly better specificity compared to ARCHITECT HIV Ag/Ab Combo (100% versus 99.7%). The 4th generation HIV Combo tests detected seroconversion 7–11 days earlier than the 3rd generation HIV antibody only EIAs.ConclusionBoth 4th generation immunoassays demonstrated excellent performance in sensitivity, with the reduction of the serological window period (7–11 days earlier detection than the 3rd generation HIV tests). However, GS HIV Combo Ag/Ab demonstrated improved HIV antigen analytical sensitivity and slightly better specificity when compared to ARCHITECT HIV Ag/Ab Combo assay, with higher positive predictive values (PPV) for low prevalence populations.     

Seven human immunodeficiency virus (HIV) antigen-antibody combination assays: evaluation of HIV seroconversion sensitivity and subtype detection

In this study, we evaluated the performance of two prototype human immunodeficiency virus (HIV) antigen-antibody (Ag-Ab) combination assays, one from Abbott Laboratories (AxSYM HIV Ag-Ab) and the other from bioMerieux (VIDAS HIV Duo Ultra), versus five combination assays commercially available in Europe. The assays were Enzygnost HIV Integral, Genscreen Plus HIV Ag-Ab, Murex HIV Ag-Ab Combination, VIDAS HIV Duo, and Vironostika HIV Uniform II Ag-Ab. All assays were evaluated for the ability to detect p24 antigen from HIV-1 groups M and O, antibody-positive plasma samples from HIV-1 groups M and O, HIV-2, and 19 HIV seroconversion panels. Results indicate that although all combination assays can detect antibodies to HIV-1, group M, subtypes A to G, circulating recombinant form (CRF) A/E, and HIV-1 group O, their sensitivity varied considerably when tested using diluted HIV-1 group O and HIV-2 antibody-positive samples. Among combination assays, the AxSYM, Murex, and VIDAS HIV Duo Ultra assays exhibited the best antigen sensitivity (at approximately 25 pg of HIV Ag/ml) for detection of HIV-1 group M, subtypes A to G and CRF A/E, and HIV-1 group O isolates. However, the VIDAS HIV Duo Ultra assay had a lower sensitivity for HIV-1 group M and subtype C, and was unable to detect subtype C antigen even at 125 pg of HIV Ag/ml. The HIV antigen sensitivity of the VIDAS HIV Duo and Genscreen Plus combination assays was approximately 125 pg of HIV Ag/ml for detection of all HIV-1 group M isolates except HIV-1 group O while the sensitivity of Vironostika HIV Uniform II Ag-Ab and Enzygnost HIV Integral Ag-Ab assays for all the group M subtypes was >125 pg of HIV Ag/ml. Among the combination assays, the AxSYM assay had the best performance for detection of early seroconversion samples, followed by the Murex and VIDAS HIV Duo Ultra assays.     

Performances of four fourth‐generation human immunodeficiency virus‐1 screening assays

Fourth‐generation human immunodeficiency virus‐1 (HIV‐1) screening assays have improved sensitivity, but vary in performance characteristics. The purpose of this study was to evaluate four different fourth‐generation HIV‐1 assays. These assays included the AxSYM HIV Ag/Ab Combo (Abbott diagnostics, Delkenheim, Germany), ARCHITECT HIV Ag/Ab Combo (Abbott), Elecsys 2010 HIV Combi (Roche Diagnostics GmbH, Mannheim, Germany), and Elecsys HIV Combi PT (Roche). A total of 1,306 samples that included 1,225 clinical samples and 81 samples consisting of seroconversion panels, an HIV‐1 p24 antigen sensitivity panel, and dilution series of HIV‐1 lysates and HIV‐1 antibodies were tested. All of the assays had sensitivities of 100% on clinical samples. The specificities of the AxSYM, ARCHITECT, Elecsys 2010 HIV Combi, and Elecsys HIV Combi PT were 99.6, 99.6, 99.0, and 99.5%, respectively. Of the 81 samples with different levels of HIV antigen or antibody and/or subtypes, Elecsys HIV Combi PT and ARCHITECT HIV Ag/Ab Combo showed better analytical sensitivities than the other two assays. In summary, the performance characteristics of AxSYM, ARCHITECT, and Elecsys HIV Combi PT were comparable and satisfactory for clinical samples. ARCHITECT HIV Ag/Ab Combo and Elecsys HIV Combi PT have the higher analytical sensitivities, and would be preferable for reducing the window period. J. Med. Virol. 84:1884–1888, 2012. © 2012 Wiley Periodicals, Inc.     

Fourth-Generation Enzyme-Linked Immunosorbent Assay for the Simultaneous Detection of Human Immunodeficiency Virus Antigen and Antibody

The VIDAS HIV DUO Ultra, a fourth-generation immunoassay under development for the simultaneous detection of human immunodeficiency virus type 1 (HIV-1) p24 antigen and antibodies to HIV-1 and HIV-2, was evaluated. The enzyme-linked fluorescence immunoassay, performed on the automated VIDAS instrument, is claimed to detect early and established HIV infection. The assay was challenged with a total of 2,847 samples that included 74 members of 10 seroconversion panels, 9 p24 antigen-only-reactive members of a panel of group M clades, 503 consecutively collected samples from individuals seeking care in the University of Maryland Medical System, 1,010 samples from U.S. blood donors, 1,141 samples from patients in a high-incidence population in Trinidad, 83 samples from a clinic for sexually transmitted diseases in the Bahamas, 10 confirmed HIV-1 group O samples, and 16 confirmed HIV-2 samples from the Cote d'Ivoire. Reference tests were U.S. Food and Drug Administration-licensed HIV antibody screening, p24 antigen tests, HIV confirmatory assays, and the Roche Diagnostics Amplicor HIV-1 Monitor. The VIDAS HIV DUO Ultra demonstrated 100% sensitivity and 99.5% specificity overall, with a 99.7% specificity in low-risk individuals. The analytical sensitivity, as assessed by seroconversion panels and p24 antigen in samples, was equivalent to the sensitivity of the reference assays used to characterize these panels. The VIDAS HIV DUO Ultra is accurate, offers potential advantages over conventional HIV testing for time and cost savings, has walk-away capability, and correctly identifies both early and established HIV infections.     

Evaluation of the performance of a new automated HIV combination assay

BackgroundMore and more countries test for HIV infection using combination assays that simultaneously detect p24 antigen and HIV antibodies.ObjectiveTo assess the performance of a new HIV combo assay: LIAISON^® XL murex HIV Ab/Ag HT.Study designThe assays were examined with a total of 3090 samples that included 769 selected HIV antibody-negative samples, 1849 unselected HIV samples, 15 HIV-1 p24 Ag reference samples, 90 primary HIV-1 infection (PHI) samples, 167 HIV-1 antibody-positive samples (well characterized of groups M and O), 95 HIV-1 antibody-positive samples and 105 HIV-2 antibody-positive samples.ResultsThe specificity of the LIAISON^® XL murex HIV Ab/Ag HT was 99.7%. The analytical sensitivity of Ag p24 of the LIAISON^® XL murex HIV Ab/Ag HT was 0.58 IU/mL and 9.93 pg/mL when using WHO and French national standards, respectively. All screened HIV subtypes was identified by this assay. Also, 90 PHI specimens were detected by this screening assay.ConclusionThe sensitivity and specificity of the LIAISON^® XL murex HIV Ab/Ag HT assay are high. Hence the assay offers automated high-throughput screening with ability to detect primary infection.     

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

BackgroundEarly 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.ObjectiveTo 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 design5029 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.ResultsOf 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.ConclusionIn 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.     

Analytical performance of the VERIS MDx system HCV assay for detecting and quantifying HCV RNA

BackgroundThe diagnosis of HCV relies on the detection of viral RNA.ObjectiveTo evaluate the performance of the VERIS/MDx System HCV Assay, a new automated system for quantifying HCV RNA, and to compare with the COBAS^® Ampliprep/COBAS^® Taqman™ (CAPCTM) HCV Test version 2.0.Study designThe limit of detection was determined by Probit analysis with the 3rd International WHO HCV standard and precision by assaying in duplicate control samples with HCV RNA concentrations of 7.9; 5.0; 3.4; 1.6 and 0 log IU/ml over 20 days. Analytical specificity was assessed by assaying 180 samples from negative anti-HCV and HCV RNA blood donors and linearity with replicates of serial dilutions of a clinical plasma (6.4–0.6 log IU/ml). We compared the VERIS MDx HCV and CAPCTM HCV assays by testing 209 samples.ResultsThe limit of detection was 6.1 IU/ml [CI 95%: 5.0–8.3] and the precision, given by the standard deviation, was ≤0.11 log IU/ml. Specificity was 100%. The linearity ranged from 1.5 to 6.4 log IU/ml. Passing-Bablok regression analysis gave: VERIS log IU/ml = −0.33 + [1.04× CAPCTM] log IU/ml, with biases for the 25th, 50th, 75th percentiles of 0.18, −0.10 and −0.06 log IU/ml. The two assays were well correlated (ρ = 0.92, p < 0.001) and Bland-Altman analysis gave biases of 0.12, log IU/ml for genotype 1, −0.19 for genotype 2, −0.26 for genotype 3, and −0.77 for genotype 4.ConclusionThe VERIS MDx HCV assay performed well. But, we observed an under-quantification of the genotype 4 samples.     

Performance of Determine Combo and other point-of-care HIV tests among Seattle MSM

Background and objectiveThe rapid test study was a real-time comparison of point-of-care (POC) HIV tests to determine their abilities to detect early HIV infection.Study designMen and transgender persons reporting sex with men in the prior year were recruited at the Public Health—Seattle & King County STD Clinic, Gay City Health Project, and University of Washington Primary Infection Clinic. Study tests included the OraQuick ADVANCE Rapid HIV-1/2 Antibody Test performed on oral fluids and tests performed on fingerstick whole blood specimens including OraQuick, Uni-Gold Recombigen HIV test, Determine HIV-1/2 Ag/Ab Combo, and INSTI HIV-1 Rapid Antibody Test. Specimens from subjects with negative results were sent for EIA and nucleic acid amplification testing. McNemar's exact tests compared the numbers of HIV-infected subjects detected.ResultsBetween February 2010 and August 2014, there were 3438 study visits. Twenty-four subjects had discordant POC results with at least one reactive and one non-reactive test, including one subject with a reactive Determine p24 antigen. OraQuick performed on oral fluids identified fewer persons compared to all fingerstick tests. OraQuick performed on fingerstick whole blood detected fewer persons compared to the Determine Combo antibody component (p = .008) and Combo overall (p = .004), and there was a trend when compared to INSTI (p = .06). The Determine Combo specificity was 98.99%.ConclusionsAs reported by others, Determine Combo underperforms compared to laboratory-based testing, but it did detect one acute infection. If these results are validated, the specificity of Determine Combo may limit its usefulness in populations with lower HIV incidence.     

Variable capacity of 13 hepatitis B virus surface antigen assays for the detection of HBsAg mutants in blood samples

BackgroundNatural variation and mutations in the envelope protein (S) of hepatitis B virus can translate into HBsAg variants no longer detectable by conventional HBsAg assays.ObjectivesThe aim of the study was to assess the performance of 13 commercial assays currently used for screening and clinical analysis of HBsAg variants.Study designThe limit of detection (LOD) for each assay was established using two reference standards (WHO HBsAg 00/588 and the SFTS French reference). Sensitivity was evaluated using different panels. Panel 1 included 25 recombinant HBs variants at three concentrations, panels 2 and 4 included 8 recombinant HBsAg variants and 9 wild-type proteins (genotypes A–F), respectively, panel 3 included 16 natural HBsAg variants.ResultsLODs ranged from 0.011 to 0.095 IU/ml with the WHO standard, and from 0.021 to 0.326 ng/ml with the French reference. The overall percentage of positive signals using HBsAg variants ranged from 62.9% to 97.9%. Three substitutions: T123, D144A and G145, were negative at all concentrations with at least one assay.DiscussionOur findings show that, although they fulfil CE requirements for analytical sensitivity (LODs below 0.13 IU/ml), HBsAg assays may vary in their capacity to detect HBsAg variants. This limit in diagnosis performance should encourage the health regulatory agencies to include HBsAg variant panels in the evaluation process.     

Diagnostic performance of serological assays for anti-HBs testing: Results from a quality assessment program

BackgroundPost-vaccination testing after hepatitis B vaccination is indispensable to evaluate long-term immunological protection. Using a threshold level of antibodies against hepatitis B surface antigen (anti-HBs) to define serological protection, implies reproducible and valid measurements of different diagnostic assays.ObjectivesIn this study we assess the performance of currently used anti-HBs assays.Study designIn 2013, 45 laboratories participated in an external quality assessment program using pooled anti-HBs serum samples around the cutoff values 10 IU/l and 100 IU/l. Laboratories used either Axsym (Abbott Laboratories), Architect (Abbott Laboratories), Access (Beckman-Coulter), ADVIA Centaur anti-HBs2 (Siemens Healthcare Diagnostics), Elecsys, Modular or Cobas (Roche Diagnostics) or Vidas Total Quick (Biomerieux) for anti-HBs titre quantification. We analysed covariance using mixed-model repeated measures. To assess sensitivity/specificity and agreement, a true positive or true negative result was defined as an anti-HBs titre respectively above or below the cutoff value by ≥4 of 6 assays.ResultsDifferent anti-HBs assays were associated with statistically significant (P < 0.05) differences in anti-HBs titres in all dilutions. Sensitivity and specificity ranged respectively from 64%-100% and 95%-100%. Agreement between assays around an anti-HBs titre cutoff value of 10 IU/l ranged from 93%-100% and was 44% for a cutoff value of 100 IU/l.ConclusionsAround a cutoff value of 10 IU/l use of the Access assay may result in false-negative results. Concerning the cutoff value of 100 IU/l, a sample being classified below or above this cutoff relied heavily on the specific assay used, with both the Architect and the Access resulting in false-negative results.     

Field evaluation of the Abbott ARCHITECT HIV Ag/Ab Combo immunoassay

BackgroundFourth generation assays for HIV diagnosis are progressively being introduced into routine services, due to their improvement of diagnosis. In spite of this, HIV diagnosis remains a challenge in sub-Saharan Africa, due to false positive reactivity. There is a continuous need for field evaluations and routine validations of fourth generation HIV tests in African populations.ObjectivesEvaluate the performances of the ARCHITECT HIV Ag/Ab kit (Abbott) in a population living in an African setting-Cameroon compared to a population living in a European setting-France.Study design645 HIV samples from both France and Cameroon were evaluated. The positive panel (378 samples) included a diverse series of HIV-1 variants (groups M, N, O, and P) as well as HIV-2 samples. Results were compared to original diagnosis done with other 4th generation assays (AxSYM HIV Ag/Ab (Abbott) and Vidas HIV DUO QUICK) (bioMérieux).ResultsSensitivity of the ARCHITECT was 100% in both sites. It diagnosed all variants of the panel with different reactivity profiles following strain diversity. A wider range of reactivity was observed for group O. Specificity was slightly lower (97.6%) in Cameroon than in France (98.6%), probably due to a higher rate of false positive reactivity. ARCHITECT HIV Ag/Ab assay had high performances in clinical sensitivity and specificity and is adapted to the wide genetic diversity of viruses circulating in West Central Africa.ConclusionOur results further highlight the need to evaluate HIV diagnostic tests before introduction into routine diagnostic services both in the North and in the South.     

Evaluation of a new automated assay for hepatitis B surface antigen (HBsAg) detection VIDAS HBsAg Ultra

In a multicenter study a new automated screening assay, VIDAS HBsAg Ultra (long (L) and short (S) incubation protocol (Biomérieux, Marcy l'Etoile, France), was compared to a well established test (AxSYM HBsAg v2, Abbott Diagnostics, Wiesbaden, Germany) for the detection of hepatitis B virus (HBV) surface antigen (HBsAg). A total of 32 seroconversion panels, sera from the chronic phase of infection, dilution series of the WHO standard, S gene mutants (recombinant mutants and diluted and undiluted sera harbouring mutants with single or multiple amino acid (aa) substitutions, n = 40) and isolated anti-HBc positive samples were tested for the evaluation of sensitivity. Sera from HBsAg negative blood donors, pregnant women, hospitalized patients and potentially cross-reactive samples were investigated to determine the specificity of the new assay. The VIDAS HBsAg Ultra (L+S) had a higher sensitivity than the alternative assay for the detection of acute hepatitis B in seroconversion panels. The mean time of the diagnostic window was shortened with the VIDAS HBsAg Ultra (L) and (S) in comparison with the AxSYM HBsAg v2 by 1.06 and 0.66 days, respectively. The VIDAS HBsAg Ultra (L) did not detect one diluted sample out of six bearing the single aa G145R substitution, and two out of 12 diluted samples harbouring multiple aa substitutions. The analytical sensitivity of the assays varied from one surface mutant to another. While no false positive results were obtained with the VIDAS HBsAg Ultra (L+S) among potentially interfering samples, four false positives were detected with the AxSYM HBsAg v2. The respective values for sensitivity for the VIDAS HBsAg Ultra (L), (S) and the AxSYM HBsAg v2 were 99.07%, 97.87% and 94.14%. The specificities were 100% (VIDAS HBsAg Ultra L and S) and 99.6% (AxSYM HBsAg v2). In conclusion, the VIDAS HBsAg Ultra is highly sensitive and specific and represents an improvement for the detection of HBsAg in routine diagnostic laboratories.     

Detection and quantification of HIV-1 RNA with a fully automated transcription-mediated-amplification assay

BackgroundNucleic acid testing is the major method used to monitor HIV viral load. Commercial systems based on real-time PCR assays are available for high-volume centralized laboratory testing, but they are not fully automated.Objectives and study designWe have compared the diagnostic performance of the Hologic Aptima HIV-1 Quant Dx assay (Aptima) (based on real-time TMA) on the Panther instrument, a fully-automated random access platform, to that of, the Roche Cobas Ampliprep Cobas TaqMan (CAP/CTM) HIV-1 version 2.0 (based on real-time PCR).ResultsProbit analysis of replicate dilutions of NIBSC WHO International HIV-1 Standard, gave LODs of 8.6 c/ml for Aptima and 15.2 c/ml for CAP/CTM. The agreement between the assays was excellent when measuring HIV RNA in a calibrated reference (κ = 0.90, p < 0.001) and good when measuring clinical samples (κ = 0.62, p < 0.001). The correlation among the samples quantified by the two methods was very good (r = 0.95, p< 0.001) and the mean difference between the values obtained with the two assays was 0.02 log c/ml for B and non-B subtypes. The vast majority of results showed <0.5 log variance between the two assays (89%); only one sample showed results that differed by over 1.0 log c/ml.ConclusionThe performance of the new fully automated Aptima assay is adequate for clinical monitoring of HIV-1 RNA during infections and treatment. The Aptima assay is well suited for routine laboratory use.     

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-linkedimmunosorbent 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.     

Evaluation of dried blood spot protocols with the Bio-Rad GS HIV Combo Ag/Ab EIA and Geenius™ HIV 1/2 Supplemental Assay

ObjectiveFDA-approved antigen/antibody combo and HIV-1/2 differentiation supplemental tests do not have claims for dried blood spot (DBS) use. We compared two DBS-modified protocols, the Bio-Rad GS HIV Combo Ag/Ab (BRC) EIA and Geenius™ HIV-1/2 (Geenius) Supplemental Assay, to plasma protocols and evaluated them in the CDC/APHL HIV diagnostic algorithm.MethodsBRC-DBS p24 analytical sensitivity was calculated from serial dilutions of p24. DBS specimens included 11 HIV-1 seroconverters, 151 HIV-1-positive individuals, including 20 on antiretroviral therapy, 31 HIV-2-positive and one HIV-1/HIV-2-positive individuals. BRC-reactive specimens were tested with Geenius using the same DBS eluate. Matched plasma specimens were tested with BRC, an IgG/IgM immunoassay and Geenius. DBS and plasma results were compared using the McNemar's test. A DBS-algorithm applied to 348 DBS from high-risk individuals who participated in surveillance was compared to HIV status based on local testing algorithms.ResultsBRC-DBS detects p24 at a concentration 18 times higher than in plasma. In seroconverters, BRC-DBS detected more infections than the IgG/IgM immunoassay in plasma (p = 0.0133), but fewer infections than BRC-plasma (p = 0.0133). In addition, the BRC/Geenius-plasma algorithm identified more HIV-1 infections than the BRC/Geenius-DBS algorithm (p = 0.0455). The DBS protocols correctly identified HIV status for established HIV-1 infections, including those on therapy, HIV-2 infections, and surveillance specimens.ConclusionsThe DBS protocols exhibited promising performance and allowed rapid supplemental testing. Although the DBS algorithm missed some early infections, it showed similar results when applied to specimens from a high-risk population. Implementation of a DBS algorithm would benefit testing programs without capacity for venipuncture.     

Evaluation of the sensitivity and specificity of six HIV combined p24 antigen and antibody assays

In this study, we evaluated the performance of six HIV combined p24 antigen and antibody (Ag/Ab) assays versus two third-generation anti-HIV antibody assays. The assays were evaluated using p24 antigen panel of 31 HIV-1 subtypes (n = 124), 25 HIV-1 seroconversion panels (n = 176), HIV-1 antibody positive samples including group M subtypes and group O (n = 559), HIV-2 positive samples (n = 110), and unselected HIV negative samples from four French private laboratories (n = 1005). The results showed that overall HIV combined Ag/Ab assays present better performance, when compared to antibody-only assays. However, some differences were observed in the sensitivity of the six HIV combined Ag/Ab assays evaluated. The AxSYM and Murex Combo assays had the best sensitivity score in this study and reduced the window period by 2.0-2.35 days relative to antibody only assays and 1-2.17 days relative to the other combined Ag/Ab assays. Among combined HIV Ag/Ab assays, Genscreen Plus and AxSYM Combo presented the highest specificity, with 99.9% and 99.8%, respectively.     

Performance of a completely automated system for monitoring CMV DNA in plasma

BackgroundCompletely automated systems for monitoring CMV-DNA in plasma samples are now available.ObjectivesEvaluate analytical and clinical performances of the VERIS™/MDx System CMV Assay^®.Study designAnalytical performance was assessed using quantified quality controls. Clinical performance was assessed by comparison with the COBAS^® Ampliprep™/COBAS^® Taqman CMV test using 169 plasma samples that had tested positive with the in-house technique in whole blood.ResultsThe specificity of the VERIS™/MDx System CMV Assay^® was 99% [CI 95%: 97.7–100]. Intra-assay reproducibilities were 0.03, 0.04, 0.05 and 0.04 log₁₀ IU/ml (means 2.78, 3.70, 4.64 and 5.60 log₁₀ IU/ml) for expected values of 2.70, 3.70, 4.70 and 5.70 log₁₀ IU/ml. The inter-assay reproducibilities were 0.12 and 0.08 (means 6.30 and 2.85 log₁₀ IU/ml) for expected values of 6.28 and 2.80 log₁₀ IU/ml. The lower limit of detection was 14.6 IU/ml, and the assay was linear from 2.34 to 5.58 log₁₀ IU/ml. The results for the positive samples were concordant (r = 0.71, p < 0.0001; slope of Deming regression 0.79 [CI 95%: 0.56–1.57] and y-intercept 0.79 [CI 95%: 0.63–0.95]). The VERIS™/MDx System CMV Assay^® detected 18 more positive samples than did the COBAS^® Ampliprep™/COBAS^® Taqman CMV test and the mean virus load were higher (0.41 log₁₀ IU/ml). Patient monitoring on 68 samples collected from 17 immunosuppressed patients showed similar trends between the two assays. As secondary question, virus loads detected by the VERIS™/MDx System CMV Assay^® were compared to those of the in-house procedure on whole blood. The results were similar between the two assays (−0.09 log₁₀ IU/ml) as were the patient monitoring trends.ConclusionThe performances of the VERIS™/MDx System CMV Assay^® facilitated its routine use in monitoring CMV-DNA loads in plasma samples.