Seroconversion Panels Research Articles

Performance evaluation of the mindray anti-HCV assay for the detection of hepatitis C virus infection.

Anti-hepatitis C virus (anti-HCV) antibody assays are recommended for HCV infection screening. The Mindray anti-HCV assay, based on a third-generation immunoassay, was recently launched in China. We aimed to evaluate its diagnostic performance compared with that of two other widely used assays. Six HCV infection seroconversion panels were used to evaluate the sensitivity of the assay for early detection. A total of 1952 clinical samples were tested by the Mindray anti-HCV, Elecsys anti-HCV II, and Architect anti-HCV assays. Samples with reactive results using at least one anti-HCV assay were further tested with the recombinant immunoblot assay (RIBA). Inconsistent results were investigated by the HCV RNA assay and HCV core antigen assay. HCV infection diagnosis was made according to the results of laboratory tests and medical records. The Mindray anti-HCV assay and Elecsys anti-HCV II assay detected seroconversion in an average of 12.5days and 10.5days, respectively, and this difference was not significant (P=.818). Of the 1952 cases, 90 were categorized as "HCV infection" and 1862 were categorized as "no HCV infection." The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) of each assay were as follows: the Mindray anti-HCV assay, 95.6%, 99.2%, 85.1%, 99.8%, 118.6 and 0.045, respectively; the Architect anti-HCV assay, 98.9%, 95.2%, 50.0%, 99.9%, 20.69 and 0.012, respectively; and the Elecsys anti-HCV II assay, 96.7%, 99.9%, 98.9%, 99.8%, 1799.9 and 0.033, respectively. There were significant differences in the specificity, PPV and LR+ among the three assays (P<.001). There were no significant differences in the sensitivity, NPV or LR- among the three assays (P>.05). The Mindray anti-HCV assay displays a similar sensitivity to the Elecsys anti-HCV II assay with respect to the early detection of HCV infection. The Mindray anti-HCV assay shows excellent diagnostic performance and is suitable for the screening of HCV infection.

Development of a Rapid Automated Fluorescent Lateral Flow Immunoassay to Detect Hepatitis B Surface Antigen (HBsAg), Antibody to HBsAg, and Antibody to Hepatitis C.

BackgroundAccurate, rapid, and cost-effective screening tests for hepatitis B virus (HBV) and hepatitis C virus (HCV) infection may be useful in laboratories that cannot afford automated chemiluminescent immunoassays (CLIAs). We evaluated the diagnostic performance of a novel rapid automated fluorescent lateral flow immunoassay (LFIA).MethodsA fluorescent LFIA using a small bench-top fluorescence reader, Automated Fluorescent Immunoassay System (AFIAS; Boditech Med Inc., Chuncheon, Korea), was developed for qualitative detection of hepatitis B surface antigen (HBsAg), antibody to HBsAg (anti-HBs), and antibody to HCV (anti-HCV) within 20 minutes. We compared the diagnostic performance of AFIAS with that of automated CLIAs—Elecsys (Roche Diagnostics GmbH, Penzberg, Germany) and ARCHITECT (Abbott Laboratories, Abbott Park, IL, USA)—using 20 seroconversion panels and 3,500 clinical serum samples.ResultsEvaluation with the seroconversion panels demonstrated that AFIAS had adequate sensitivity for HBsAg and anti-HCV detection. From the clinical samples, AFIAS sensitivity and specificity were 99.8% and 99.3% for the HBsAg test, 100.0% and 100.0% for the anti-HBs test, and 98.8% and 99.1% for the anti-HCV test, respectively. Its agreement rates with the Elecsys HBsAg, anti-HBs, and anti-HCV detection assays were 99.4%, 100.0%, and 99.0%, respectively. AFIAS detected all samples with HBsAg genotypes A-F and H and anti-HCV genotypes 1, 1a, 1b, 2a, 2b, 4, and 6. Cross-reactivity with other infections was not observed.ConclusionsThe AFIAS HBsAg, anti-HBs, and anti-HCV tests demonstrated diagnostic performance equivalent to current automated CLIAs. AFIAS could be used for a large-scale HBV or HCV screening in low-resource laboratories or low-to middle-income areas.

An ultra-sensitive Abbott ARCHITECT® assay for the detection of hepatitis B virus surface antigen (HBsAg)

BackgroundCritical to the identification of HBV infection and the prevention of transfusion transmitted disease is the sensitive and accurate detection of Hepatitis B virus surface antigen (HBsAg). Improvements in HBsAg assay sensitivity approaching the performance of nucleic acid testing (NAT) are essential to further reduce the detection window for acute HBV infection in regions where NAT is not widely available. Objectives and study designAn improved HBsAg assay on the fully-automated Abbott ARCHITECT® platform was developed to improve sensitivity, mutant and genotype detection. ResultsThe analytical sensitivity of the improved prototype assay is 5.2 mIU/ml, which is 3.86- to 14.54-fold more sensitive than comparator assays based on the WHO International Reference Standard. The enhanced sensitivity was also demonstrated with 27 HBV seroconversion panels, detecting more panel members (191 of 364) vs. the ARCHITECT® Qual I (144), Qual II (160) and PRISM® (148) HBsAg assays. Further, the assay detected 7 of 12 HBV DNA positive/HBsAg negative samples, and detected all evaluated mutants and genotypes with higher sensitivity than the comparator assays. The improvement in sensitivity did not diminish assay specificity, attaining 100% (95% CI, 99.97-100%) on 10,633 blood donors. ConclusionsAn Abbott ARCHITECT® HBsAg assay with clinical performance approaching that of mini-pool NAT (approximately 100 copies/ml was developed. The assay has superior HBsAg mutant and genotype detection and specificity, all of which are important for the diagnosis and management of HBV infection.

P-E3 Assessment of internationally-available HIV test kits for their suitability to meet manufacturers' claims

Background: HIV test kits, particularly rapid HIV tests, are used throughout the world as a primary measure to protect the blood supply and provide diagnosis to save lives. The US government purchases large numbers of HIV tests at considerable expense, and expects them to perform adequately. Objective: To assess a large number and variety of HIV test kits to determine if they meet the claims of the manufacturers. Methods: From September 2010 through July 2017, a total of 1,123 lots of HIV test kits from 14 manufacturers and representing 11 different tests from 26 countries, were received for evaluation at the INSTITUTE OF HUMAN VIROLOGY. Each test kit was assessed for performance characteristics using panels of sera (n=30 or 160) that included positives for HIV-1 and HIV-2 (n=8 or 80), and negatives (n=22 or 80). Several HIV-1 positive samples were weak positives derived from seroconversion panels (SeraCare). Test kits were also assessed for precision using several HIV-1 weak positive samples tested in replicate. Results: Of the HIV test kit lots evaluated, 99.2% successfully passed the evaluation with perfect performance. Of the 9 lots that did not pass, 3 were found to produce high background that interfered with reading, 2 performed inadequately with high-temperature testing, and 4 exhibited greater than one false-positive result. In one assessment, a country had reported poor performance of a test kit, but the test kit passed the evaluation; this resulted in a visit to the country to assess the laboratory's activities. Conclusion: In our evaluation of a large number and variety of HIV test kit lots from 14 manufacturers, nearly all performed as expected and met the manufacturers' claims.

Brazilian Program For HIV Point-Of-Care Test Evaluation: A Decade’s Experience

The point-of-care tests (POCTs) for HIV diagnosis have been widely used in Brazil in order to expand and to allow HIV diagnosis outside health units including remote areas, such as the Amazon region. In order to guarantee the quality of HIV diagnostics based on rapid tests, the Brazilian Ministry of Health (MoH) implemented the HIV POCT Evaluation Program. This study compiles the Brazilian experience acquired over the last 13 years conducting the HIV POCT Evaluation Program.&#x0D; &#x0D; Methods and Findings&#x0D; The selection of tests was based on the interest of manufacturers to qualify for the MoH tenders. Each round was performed with fresh whole blood and oral fluid samples, always including HIV positive and negative ones. In addition to the POCT, every sample was submitted to a reference testing protocol, based on an immunoassay followed by Western blot. The POCTs were evaluated for clinical sensitivity, clinical specificity, assay operational characteristics, detection of HIV-2 antibodies, sensitivity to subtypes panels; and sensitivity to seroconversion panels. Since its implementation in 2003, the POCT evaluation protocol has undergone some modifications aiming to improve and simplify the evaluation process, to know: (i) for HIV-positive samples, perform EIA and Western blot only if the POCT is non-reactive; (ii) reduction from 800 to 600 HIV negative samples; (iii) increase from one to three subtype panels (including HIV-2 samples); and (iv) inclusion of seroconversion panel. We evaluated six tests, four of which met the sensitivity criteria of 99.5%: BD Chek™ HIV Multi-test (whole blood), HIV 1/2 Colloidal Gold (whole blood), OraQuick ADVANCE® Rapid HIV-1/2 Antibody Test (whole blood and oral fluid) and TR DPP HIV-1/2 (whole blood, plasma and oral fluid). Regarding other evaluated criteria, all assays met the requirements.&#x0D; &#x0D; Conclusions&#x0D; The successful Brazilian policy on POCT use for HIV infection diagnosis includes the evaluation of the POCT itself in addition to appropriate selection of tests to be acquired and nationwide distributed to the public health facilities, control of each test batch distributed by the MoH, proper and easily accessible training to all health professionals involved in rapid testing through distance learning tools, and continued evaluation of POCT use through external quality assessment.

Evaluation of the highly sensitive chemiluminescent enzyme immunoassay "Lumipulse HBsAg-HQ" for hepatitis B virus screening.

Ongoing efforts in the development of HBsAg detection kits are focused on improving sensitivity and specificity. The purpose of this study was to evaluate an improved, highly sensitive quantitative assay, "Lumipulse HBsAg-HQ", a chemiluminescent enzyme immunoassay designed for a fully automated instrument, the "Lumipulse G1200". Serum samples for reproducibility, dilution, correlation, sensitivity, and specificity studies were obtained from patients at the Osaka University Hospital. Seroconversion and sensitivity panels were purchased from a commercial vender. Subtype, sensitivity panels, and HBsAg recombinant proteins with one or two amino acid substitutions were prepared in-house. The coefficients of variation for the low, medium, and high concentration samples ranged from 1.93 to 2.55%. The HBsAg-HQ reagent for dilution testing showed good linearity in the 0.005-150 HBsAg IU/mL range and no prozone phenomenon. All 102 HBV carrier samples were positive by HBsAg-HQ, while other commercial reagents showed one or more to be negative. In the seroconversion panel, the 14-day blood sample was positive. The sensitivity against HBsAg-HQ "ad" and "ay" subtypes was 0.025ng/mL. Comparisons among the HBsAg-HQ, HISCL, and Architect HBsAg reagents were performed using the Bland-Altman plot. Specificity for 1000 seronegative individuals was 99.7%. HBsAg-HQ detected 29 positive serum among 12231 routinely obtained serum samples, which showed concentrations of 0.005-0.05 HBsAg IU/mL. According to these results, the Lumipulse HBsAg-HQ assay, with a highly sensitive limit of detection of 0.005 IU/mL, may facilitate the development of a better management strategy for a considerable proportion of infected patients.

Chimeric rabbit/human Fab antibodies against the hepatitis Be-antigen and their potential applications in assays, characterization, and therapy

Hepatitis B virus (HBV) infection afflicts millions worldwide, causing cirrhosis and liver cancer. HBV e-antigen (HBeAg), a clinical marker for disease severity, is a soluble variant of the viral capsid protein. HBeAg is not required for viral replication but is implicated in establishing immune tolerance and chronic infection. The structure of recombinant e-antigen (rHBeAg) was recently determined, yet to date, the exact nature and quantitation of HBeAg still remain uncertain. Here, to further characterize HBeAg, we used phage display to produce a panel of chimeric rabbit/human monoclonal antibody fragments (both Fab and scFv) against rHBeAg. Several of the Fab/scFv, expressed in Escherichia coli, had unprecedentedly high binding affinities (Kd ∼10-12 m) and high specificity. We used Fab/scFv in the context of an enzyme-linked immunosorbent assay (ELISA) for HBeAg quantification, which we compared with commercially available kits and verified with seroconversion panels, the WHO HBeAg standard, rHBeAg, and patient plasma samples. We found that the specificity and sensitivity are superior to those of existing commercial assays. To identify potential fine differences between rHBeAg and HBeAg, we used these Fabs in microscale immunoaffinity chromatography to purify HBeAg from individual patient plasmas. Western blotting and MS results indicated that rHBeAg and HBeAg are essentially structurally identical, although HBeAg from different patients exhibits minor carboxyl-terminal heterogeneity. We discuss several potential applications for the humanized Fab/scFv.

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

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

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

BackgroundThe Determine™ HIV-1/2 Ag/Ab Combo (DC) rapid test can identify HIV-1 infection earlier than rapid antibody-only tests in plasma specimens. ObjectivesWe compared the performance of DC with a laboratory-based antigen/antibody (Ag/Ab) combo assay in plasma and evaluated antigen reactivity in whole blood specimens. Study designWe tested by DC 508 plasma specimens collected in a prospective study and 107 sequential plasma and simulated whole blood specimens from 20 seroconversion panels. Previous results using the ARCHITECT (ARC) Ag/Ab combo assay were compared to DC results. In seroconversion panels, the days from the first HIV1 RNA-positive test to first DC-reactive in plasma and whole blood was compared. McNemar’s and Wilcoxon signed rank tests were used for statistical analysis. ResultsOf 415 HIV-positive samples, ARC detected 396 (95.4%) and DC 337 (81.2%) (p<0.0001). DC was reactive in 50.0% of ARC-reactive/MS-negative, 78.6% of ARC-reactive/MS-indeterminate, and 99.6% of ARC-reactive/MS-HIV-1-positive or −undifferentiated specimens. DC antigen reactivity was higher among ARC-reactive/MS-negative than MS-indeterminate samples. In 20 HIV-1 seroconversion panels, there was a significant difference between DC reactivity in plasma (91.1%) and whole blood (56.4%) (p<0.0001). DC with whole blood showed a significant delay in reactivity compared to plasma (p=0.008). ConclusionsIn plasma, DC was significantly less sensitive than an instrumented laboratory-based Ag/Ab combo assay. DC in plasma was significantly more sensitive compared to whole blood in early HIV-1 infections. With the U.S. laboratory-based diagnostic algorithm, DC as the first step would likely miss a high proportion of HIV-1 infections in early stages of seroconversion.

Performance evaluation of the point-of-care INSTI™ HIV-1/2 antibody test in early and established HIV infections

BackgroundThe flow-through INSTI™ HIV-1/HIV-2 Rapid Antibody (INSTI) test is a 60s FDA-approved test for HIV-1 and HIV-2 antibody testing using whole blood and plasma. ObjectiveWe evaluated the performance of INSTI using plasma and simulated whole blood specimens. Study designINSTI’s performance in plasma specimens from commercial seroconversion panels was assessed by estimating the relative sensitivity using a 50% cumulative frequency analysis and by comparing its performance with other FDA-approved rapid tests (RTs). INSTI was further evaluated using 320 HIV-1 plasma specimens collected during a cross-sectional study and with 107 HIV-1 and 24 HIV-2 simulated whole blood specimens. Sensitivity and specificity were calculated using 615 known HIV-1 group M/O and 80 HIV-2 (Western blot (WB)-positive), and 497 HIV-negative plasma specimens, respectively. ResultsIn HIV-1 seroconversion panels, INSTI became reactive 9days before a positive WB. When compared to FDA-approved antibody-based lateral flow RTs, INSTI detected significantly more early infections. Among HIV-1-infected cross-sectional plasma samples, INSTI detected 23 (27%) of 85 Architect-positive/Multispot-negative or indeterminate specimens. For plasma specimens, the sensitivity was 99.84% for HIV-1 and 100% for HIV-2, and the specificity was 99.80%. Using simulated whole blood from seroconverters, INSTI performed similarly to plasma. ConclusionsINSTI performed significantly better than antibody-based lateral flow RTs during early stages of seroconversion. Sensitivity and specificity were within the manufacturer’s reported ranges. Considering the observed test performance and the almost immediate results, INSTI is an accurate option to detect HIV-1/HIV-2 antibodies in point-of-care settings where lab testing is not feasible.

Application of ELISA kit for the detection of hepatitis E virus antigen in plasma donations

Objective To analyze the practicability of using ELISA kit for the detection of hepatitis E virus antigen (HEV-Ag) in plasma donations and Biomex HEV seroconversion panels. Methods The HEV-Ag positive samples were screened out from 36 340 donated blood plasma samples. Real-time fluorescent PCR was performed for the detection of HEV RNA in HEV-Ag positive samples. The open reading frame 2 (ORF2) in HEV RNA was amplified by nested RT-PCR and the amplified products were confirmed by sequencing analysis. Phylogenetic tree was constructed for HEV genotyping. Five Biomex HEV seroconversion panels were used in this study for the detection of HEV-Ag, anti-HEV antibody and HEV RNA as well as the correlation analysis between HEV-Ag and HEV RNA. Results Twenty-six out of 36 340 plasma samples (0.07%) were positive for HEV-Ag. Of the 26 samples, 25 samples were positive for HEV RNA as indicated by the results of nested RT-PCR and 23 positive samples were confirmed by sequencing analysis. The positive rate of HEV RNA in blood plasma donators was 1∶1 580 (0.06%). There were 17 samples of genotype 1 (74%) and 6 samples of genotype 4 (26%) according to the phylogenetic tree analysis. All of the HEV-Ag positive samples were also positive for HEV RNA as indicated by the analysis of Biomex seroconversion panels. HEV-Ag was consistent with the peak of the HEV RNA concentration. Conclusion A close relationship between HEV-Ag and HEV RNA was observed. HEV-Ag screening could be used as a measure to reduce the risk of HEV transmission by blood transfusion. Key words: Hepatitis E virus (HEV); Antigen; RNA; Plasma

Multicenter clinical evaluation of the new 3rd generation assay for detection of antibodies against hepatitis C virus on the VIDAS® system

BackgroundDetection of antibodies (anti-HCV) against hepatitis C virus (HCV) is indispensable for screening and diagnosis of viral hepatitis and for the viral safety of blood, tissue or organ donations. It gains additional importance by the new HCV drugs which improve the therapeutic possibilities dramatically. ObjectiveTo evaluate the performance of a newly developed immune assay for anti-HCV based on the well-established VIDAS platform. Study designThe assay was evaluated with samples from anti-HCV negative blood donors and from patients with or without HCV markers in six centres in France, Spain and Egypt. The status of the samples was determined by using CE-marked immune assays (Architect, AxSym, Prism, Vitros), two immunoblots (RIBA, Inno-Lia) and/or HCV RNA results. ResultsSpecificity was 99.67% in 10,320 French blood donors without anti-HCV, 99.5% in 200 anti-HCV negative hospitalized European patients and 99.0% in 198 negative patients from Egypt. Sensitivity was 99.7% in 1054 patients pretested positive by other assays; 345 patients with known genotype had genotype 1–6; 61 patients were co-infected with HIV. VIDAS was reactive in 78% of 91 patients with uncertain or very weak anti-HCV. It became on average positive at day 37 with seroconversion panels. ConclusionsThis multicentric, international study with >12,000 samples show that the new VIDAS anti-HCV assay is very suitable for screening and confirmation of HCV infection. Sensitivity, specificity and recognition of seroconversion compare favorably with well-established CE-marked tests and help to clarify discrepant results obtained with other assays.

Aptima HIV-1 Quant Dx—A fully automated assay for both diagnosis and quantification of HIV-1

BackgroundSeparate assays are available for diagnosis and viral load (VL) monitoring of HIV-1. Studies have shown that using a single test for both confirmatory diagnosis and VL increases linkage to care. ObjectiveTo validate a single assay for both diagnosis and VL monitoring of HIV-1 on the fully automated Panther platform. Study designValidate the assay by assessing specificity, sensitivity, subtype detection, seroconversion, reproducibility and linearity. Also assess diagnostic agreement with the Procleix® Ultrio Elite™ discriminatory assay (Procleix), and agreement of VL results (method comparison) with Ampliprep/COBAS TaqMan HIV-1 version 2.0 (CAP/CTM), using clinical samples. ResultsThe assay was specific (100%) and sensitive with a 95% limit of detection of 12 copies/mL with the 3rd WHO standards. Aptima detected HIV in seroconversion panels 6 and 11 days before p24 antigen and antibody tests, respectively. Diagnostic agreement with Procleix, was 100%. Regression analysis showed good agreement of VL results between Aptima and CAP/CTM with a slope of 1.02, intercept of 0.07, and correlation coefficient (R2) of 0.97. Aptima was more sensitive than CAP/CTM. Equivalent quantification was seen on testing clinical samples and isolates belonging to HIV group M, N, O and P and commercially available subtype panels. Assay results were linear (R2 0.9994) with standard deviation of <0.17 log copies across assay range. ConclusionsThe good specificity, sensitivity, precision, subtype performance and clinical agreement with other assays demonstrated by Aptima combined with the complete automation provided by the Panther platform makes Aptima a good candidate for both VL monitoring and diagnosis of HIV-1.

Comparison of Elecsys Anti-HCV II Assay With Other HCV Screening Assays.

Early detection of hepatitis C virus (HCV) is an important step in preventing progression to cirrhosis and hepatocellular carcinoma. Serologic assays for anti-HCV antibody are valuable first-line tests in the screening and diagnosis of HCV infection. This study's aim was to evaluate the sensitivity and specificity of Elecsys Anti-HCV II assay for HCV screening. A total of 1,044 routine sera, 20 known HCV-positive samples, plus 54 preselected weakly positive samples were tested for anti-HCV with Elecsys Anti-HCV II assay, Elecsys Anti-HCV assays, InTec HCV enzymoimmunoassay (EIA), and Livzon Anti-HCV EIA. Interference test was assessed with additional 423 specimens without clinical evidence of HCV infection: preselected HCV weak reactive samples; dialysis samples; anti-HBc (antibody to HBV core antigen) (+), anti-Treponema pallidum (+), and anti-HIV (+) sera; and samples form autoimmune/alcoholic hepatitis or systemic Lupus erythematosus (SLE). Discrepant results were evaluated with recombinant immunoblot assay. The seroconversion panels were evaluated to assess how early each assay could detect HCV infection. The specificity (99.81%) of the Elecsys Anti-HCV II assay was less than that with the two EIA comparison methods. However, false-negative results were easily seen in the EIA assays. When serial bleeds of HCV panels were compared with the above-mentioned methods, the assay detected acute HCV infection only 3.5 days after a positive HCV-RNA nucleic acid test and earlier than the comparator assays. Sensitivities and specificities of the anti-HCV assays were sufficiently high for use in this study. The Elecsys Anti-HCV II assay is suitable for screening and reliable early detection of HCV infection.

Anti-HCV immunoassays based on a multiepitope antigen and fluorescent lanthanide chelate reporters

There is a need for simple to produce immunoassays for hepatitis C virus (HCV) antibody capable of detecting all genotypes worldwide. Current commonly used third generation immunoassays use three to six separate recombinant proteins or synthetic peptides. We have developed and expressed in Escherichia coli a single recombinant antigen incorporating epitopes from different HCV proteins. This multiepitope protein (MEP) was used to develop two types of HCV antibody immunoassays: a traditional antibody immunoassay using a labeled secondary antibody (indirect assay) and a double-antigen assay with the same MEP used as capture binder and labeled binder. The secondary antibody assay was evaluated with 171 serum/plasma samples and double-antigen assay with 148 samples. These samples included an in-house patient sample panel, two panels of samples with different HCV genotypes and a seroconversion panel. The secondary antibody immunoassay showed 95.6% sensitivity and 100% specificity while the double-antigen assay showed 91.4% sensitivity and 100% specificity. Both assays detected samples from all six HCV genotypes. The results showed that combining a low-cost recombinant MEP binder antigen with a high sensitivity fluorescent lanthanide reporter can provide a sensitive and specific immunoassay for HCV serology. The results also showed that the sensitivity of HCV double-antigen assays may suffer from the low avidity immune response of acute infections.

Evaluation of a novel chemiluminescent microplate enzyme immunoassay for hepatitis B surface antigen detection

Hepatitis B virus surface antigen (HBsAg) is an important biomarker used in the diagnosis of hepatitis B virus (HBV) infection, but false-negative results are still reported in the detection of HBsAg using commercial assays. In this study, we evaluated the qualitative properties of a novel HBsAg chemiluminescence enzyme immunoassay (CLEIA) assay – WTultra. WHO standard sample dilution series and samples from low-level HBsAg carriers (<1ng/mL) were used to evaluate the sensitivity of the WTultra assay. Boston Biomedica, Inc. (BBI) hepatitis B seroconversion panels were used to assess the ability of the WTultra assay to detect the window period. In addition, dilution series of 22 serum samples with different genotypes, serotypes and HBsAg mutations were used to assess the WTultra assay, and these were compared with other commercial assays. The lower detection limit of the WTultra assay was 0.012IU/mL, and it showed a high sensitivity (97.52%, 95% CI, 94.95–99.00) in the detection of 282 low-level HBsAg carriers (<1ng/mL). In samples with various HBV genotypes, serotypes and HBsAg mutations, the WTultra assay yielded 117 positive results in 132 samples, which was significantly higher than the results with the other four commercial assays (89, 83, 65 and 45, respectively, p<0.01). In the assays of mutant strains, the WTultra assay detected 82 positive results in 90 samples, which was significantly better than the results for the Hepanostika HBsAg Ultra (58 positive) and Architect (55 positive) (p<0.01) assays, which in turn were significantly better than the Murex V.3 (41 positive, p=0.026) and AxSYM V2 (29 positive, p<0.01) assays. However, in the detection of 42 samples of wild-type strains with various genotypes and serotypes, no significant differences were observed among the WTultra (35 positive), Architect (28 positive) and Hepanostika HBsAg Ultra (31 positive) assays. However, the WTultra assay detected significantly more samples than the Murex V.3 (24 positive, p<0.01) and AxSYM V2 (16 positive, p<0.01) assays. In conclusion, the WTultra HBsAg assay has a high detection sensitivity and presents excellent results for the detection of mutants.

Assessment of a new "DS-EIA-HIV-AB-TERM" assay to determine the probable time of infection with human immunodeficiency virus-1 (HIV-1)

The epidemiological situation for HIV infection in Russia remains to be extremely stringent, which requires a search for new, more efficient and cost-effective solutions aimed at countering the epidemic. The inclusion of laboratory studies with the use of a test system for the determination of the remoteness of HIV infection in routine surveillance practices will permit to determine the frequency of occurrence of early cases of infections among newly diagnosed HIV-positive persons. The analysis of this criterion at the population level will help to objectively evaluate the effectiveness of prevention, control activities carried out in a particular area. The increase of objectivity in the determination of the time elapsed from the moment of infection of HIV-1 with the use of the test system DSEIA-HIV-Ab-TERM provides the opportunity to use the obtained results in the epidemiological investigation for the purpose of more accurate and complete identification of contact persons. The determination of the probable period of infection may also be required in the solving the question on the prescription of antiretroviral therapy as a complementary study in the monitoring of HIV drug resistance. The aim of this work was to determine the effectiveness of the new test system DS-EIAHIV-Ab-TERM for the determination of the likely timing of HIV-1 infection. There were studied serum samples (plasma) of blood of HIV-infected persons with epidemiologically established time of infection (n = 281) and samples of commercial seroconversion panels. Results of the performed study showed that the probability of a correct detection of the remoteness of HIV-1 infection for samples from individuals with the most probable time of the established fact of infection was 95%, for samples of commercial seroconversion panels - 100%. The data demonstrated the high efficacy of the test system DS-“EIAHIV-Ab-TERM” in the determination of the most probable timing of infection with human immunodeficiency virus type 1, that in combination with the speed and simplicity of the procedure allows to recommend it for use in the laboratory practice.

Multicenter evaluation of the Elecsys Toxo IgG and IgM tests for the diagnosis of infection with Toxoplasma gondii.

Detection of IgG and IgM antibodies is commonly performed for the diagnosis of infection with Toxoplasma gondii. We determined the accuracy of the Elecsys Toxo IgG and IgM test at four European laboratories compared to local reference methods. Coefficients of variation for reproducibility ranged from 1.0 to 6.5% for IgG and from 0.8 to 3.2% for IgM. Seroconversion panels revealed high overall concordance with the reference tests. The Elecsys test detected IgG antibodies earlier than the Cobas Core IgG test in 19 of 47 panels; persisting IgM antibodies were observed in the VIDAS but not the Elecsys test in five of 47 panels. In 31.4% of latent stage sera with persistent IgM antibodies (positive LIASON IgM), the Elecsys IgM test gave negative results indicating increased “clinical” specificity. Sensitivity and specificity of the Elecsys IgG assay ranged from 99.45 to 100% and 87.50–99.80%, respectively, and 91.11–95.74 and 98.45–99.79% for the Elecsys IgM assay, respectively.In conclusion, excellent reproducibility and accuracy make the Elecsys Toxo G and M tests highly suitable for the detection of anti-T. gondii IgG and IgM antibodies. The lower detection rates for persistent IgM in the Elecsys IgM test increase “clinical” specificity and decrease the need for follow-up testing.

Diagnostic accuracy of point-of-care tests for hepatitis C virus infection: a systematic review and meta-analysis.

BackgroundPoint-of-care tests provide a plausible diagnostic strategy for hepatitis C infection in economically impoverished areas. However, their utility depends upon the overall performance of individual tests.MethodsA literature search was conducted using the metasearch engine Mettā, a query interface for retrieving articles from five leading medical databases. Studies were included if they employed point-of-care tests to detect antibodies of hepatitis C virus and compared the results with reference tests. Two reviewers performed a quality assessment of the studies and extracted data for estimating test accuracy.FindingsThirty studies that had evaluated 30 tests fulfilled the inclusion criteria. The overall pooled sensitivity, specificity, positive likelihood-ratio, negative likelihood-ratio and diagnostic odds ratio for all tests were 97.4% (95% CI: 95.9–98.4), 99.5% (99.2–99.7), 80.17 (55.35–116.14), 0.03 (0.02–0.04), and 3032.85 (1595.86–5763.78), respectively. This suggested a high pooled accuracy for all studies. We found substantial heterogeneity between studies, but none of the subgroups investigated could account for the heterogeneity. Genotype diversity of HCV had no or minimal influence on test performance. Of the seven tests evaluated in the meta-regression model, OraQuick had the highest test sensitivity and specificity and showed better performance than a third generation enzyme immunoassay in seroconversion panels. The next highest test sensitivities and specificities were from TriDot and SDBioline, followed by Genedia and Chembio. The Spot and Multiplo tests produced poor test sensitivities but high test specificities. Nine of the remaining 23 tests produced poor test sensitivities and specificities and/or showed poor performances in seroconversion panels, while 14 tests had high test performances with diagnostic odds ratios ranging from 590.70 to 28822.20.ConclusionsPerformances varied widely among individual point-of-care tests for diagnosis of hepatitis C virus infection. Physicians should consider this while using specific tests in clinical practice.

Recalibration of the limiting antigen avidity EIA to determine mean duration of recent infection in divergent HIV-1 subtypes.

BackgroundMean duration of recent infection (MDRI) and misclassification of long-term HIV-1 infections, as proportion false recent (PFR), are critical parameters for laboratory-based assays for estimating HIV-1 incidence. Recent review of the data by us and others indicated that MDRI of LAg-Avidity EIA estimated previously required recalibration. We present here results of recalibration efforts using >250 seroconversion panels and multiple statistical methods to ensure accuracy and consensus.MethodsA total of 2737 longitudinal specimens collected from 259 seroconverting individuals infected with diverse HIV-1 subtypes were tested with the LAg-Avidity EIA as previously described. Data were analyzed for determination of MDRI at ODn cutoffs of 1.0 to 2.0 using 7 statistical approaches and sub-analyzed by HIV-1 subtypes. In addition, 3740 specimens from individuals with infection >1 year, including 488 from patients with AIDS, were tested for PFR at varying cutoffs.ResultsUsing different statistical methods, MDRI values ranged from 88–94 days at cutoff ODn = 1.0 to 177–183 days at ODn = 2.0. The MDRI values were similar by different methods suggesting coherence of different approaches. Testing for misclassification among long-term infections indicated that overall PFRs were 0.6% to 2.5% at increasing cutoffs of 1.0 to 2.0, respectively. Balancing the need for a longer MDRI and smaller PFR (<2.0%) suggests that a cutoff ODn = 1.5, corresponding to an MDRI of 130 days should be used for cross-sectional application. The MDRI varied among subtypes from 109 days (subtype A&D) to 152 days (subtype C).ConclusionsBased on the new data and revised analysis, we recommend an ODn cutoff = 1.5 to classify recent and long-term infections, corresponding to an MDRI of 130 days (118–142). Determination of revised parameters for estimation of HIV-1 incidence should facilitate application of the LAg-Avidity EIA for worldwide use.