Pre-analytical considerations in the development of a prototype SARS-CoV-2 antigen ARCHITECT automated immunoassay.

OBJECTIVES: To evaluate pre-analytical challenges related to high-volume central laboratory SARS-CoV-2 antigen testing with a prototype qualitative SARS-CoV-2 antigen immunoassay run on the automated Abbott ARCHITECT instrument. METHODS: Contrived positive and negative specimens and de-identified nasal and nasopharyngeal specimens in transport media were used to evaluate specimen and reagent on-board stability, assay analytical performance and interference, and clinical performance. RESULTS: TCID50/mL values were similar for specimens in various transport media. Inactivated positive clinical specimens and viral lysate (USA-WA1/2020) were positive on the prototype immunoassay. Within-laboratory imprecision was ≤0.10 SD (<1.00 S/C) with a ≤10% CV (≥1.00 S/C). Assay reagents were stable on board the instrument for 14 days. No high-dose hook effect was observed with a SARS-CoV-2 stock of Ct 13.0 (RLU>1.0 × 106). No interference was observed from mucin, whole blood, 12 drugs, and more than 20 cross-reactants. While specimen stability was limited at room temperature for specimens with or without viral inactivation, a single freeze/thaw cycle or long-term storage (>30 days) at -20 °C did not adversely impact specimen stability or assay performance. Specificity of the prototype SARS-CoV-2 antigen immunoassay was ≥98.5% and sensitivity was ≥89.5% across two ARCHITECT instruments. Assay sensitivity was inversely correlated with Ct and was similar to that reported for the Roche Elecsys® SARS-CoV-2 Ag immunoassay. CONCLUSIONS: The prototype SARS-CoV-2 antigen ARCHITECT immunoassay is sensitive and specific for detection of SARS-CoV-2 in nasal and nasopharyngeal specimens. Endogenous proteases in mucus may degrade the target antigen, which limits specimen storage and transport times and complicates assay workflow.

Comparison of a hepatitis C core antigen assay to nucleic acid amplification testing for detection of hepatitis C viremia in a US population.

The prevalence of hepatitis C virus (HCV) infection in the United States has increased over the past decade despite the development of effective direct-acting antiviral treatments. To meet the World Health Organization's (WHO) goal of eliminating HCV infection by 2030, transmission events must be reduced. Currently, infection screening relies on detection of HCV antibodies, with nucleic acid amplification testing (NAAT) used to confirm HCV viremia and monitor changes in viral load. However, the seroconversion window for detection of HCV antibodies is long, averaging 6 weeks, with delayed seroconversion common in co-infected and immunosuppressed populations. Testing for HCV core antigen, which is present approximately 5 weeks before HCV antibodies, holds promise for earlier detection of HCV infection. It may also hold promise as a cheaper, more accessible, and more rapid alternative to NAAT for infection confirmation. Here, we evaluated the agreement between a research-use HCV Core Antigen Assay and NAAT among US patients receiving clinically indicated NAAT. Among 412 specimens, the overall concordance was 97.1%, with a positive percent agreement of 95.5%. Discrepancies primarily occurred among patients with chronic HCV and low viral loads; 11/12 discrepancies showed viral loads <4,000 IU/mL. Among patients being screened for HCV infection (i.e., excluding those undergoing NAAT for serial monitoring of a previously diagnosed infection), the positive percent agreement was 97.0%. Among patients undergoing serial testing, changes in HCV Core Antigen Assay signal-to-cut-off values were generally correlated with changes in the viral load. Results suggest that the research-use HCV Core Antigen Assay studied here may reliably detect and/or confirm HCV infection. IMPORTANCE: A research-use HCV Core Antigen Assay showed high concordance with nucleic acid amplification testing for the detection of current hepatitis C infection. The assay may enable more rapid and lower-cost detection and/or confirmation of hepatitis C infection.

MicroRNAs are associated with cardiac biomarkers, cardiac structure and function and incident outcomes in heart failure.

AIMS: The association between microRNAs (miRNAs) and established cardiac biomarkers is largely unknown. We aimed to measure the association between plasma miRNAs and N-terminal pro-B-type natriuretic peptide (NT-proBNP), cardiac troponin I, soluble urokinase-type plasminogen activator receptor (suPAR), and galectin-3 with cardiac structure and function and clinical outcomes. METHODS AND RESULTS: We quantified 32 plasma miRNAs using the FirePlex miRNA assay and measured biomarkers in 139 individuals with symptomatic heart failure (HF). We used principal component (PC) analysis and linear regression to evaluate the association between miRNAs and biomarkers with ventricular size and function by echocardiography and Cox modelling for the incidence of a first composite event of HF hospitalization, heart transplant, left ventricular assist device implant, or death. The mean (standard deviation) age at baseline was 64.3 (12.4) years, 33 (24%) were female, and 122 (88%) were White. A total of 45 events occurred over a median follow-up of 368 (interquartile range 234, 494) days. Baseline NT-proBNP (ß = -2.0; P = 0.001) and miRNA PC2 (ß = 2.6; P = 0.002) were associated with baseline left ventricular ejection fraction. NT-proBNP (ß = 20.6; P = 0.0004), suPAR (ß = -39.6; P = 0.005), and PC4 (ß = 21.1; P = 0.02) were associated with baseline left ventricular end-diastolic volumes. NT-proBNP [hazard ratio (HR) 1.67, 95% confidence interval (CI) 1.28-2.18, P = 0.0002], galectin-3 (HR 2.02, 95% CI 1.05-3.91, P = 0.036), PC3 (HR 1.75, 95% CI 1.23-2.49, P = 0.002), and PC4 (HR 1.67, 95% CI 1.1-2.52, P = 0.016) were independently associated with incident events. CONCLUSIONS: Biomarkers and miRNA PCs are associated with cardiac structure and function and incident cardiovascular outcomes. Combining information from miRNAs provides prognostic information beyond biomarkers in HF.

Performance evaluation of the Abbott Alinity Hepatitis C antigen next assay in a US urban emergency department population.

INTRODUCTION: HCV antibody assays have been used to screen for HCV, but confirmation of acute infection is dependent on RNA or core antigen testing. The aim of the study was to compare the performance of five HCV test methods, including RNA testing, on a US emergency department population. METHODS: Clinical performance metrics were calculated on 708 consenting Johns Hopkins Emergency Department patients who self-reported an increased risk for HCV infection. Detection times of antibody, antigen, and RNA testing were compared using 89 samples from commercially available seroconversion panels. Testing was performed on the Abbott Alinity HCV Ag Next (RUO), Roche Elecsys HCV Duo, Abbott ARCHITECT Anti-HCV, and Elecsys Anti-HCV II assays. RNA testing was performed on the Abbott m2000 system. RESULTS: Overall, 21 (3.0%) participants tested positive for HCV on at least one test, 11 (52.4%) had chronic, 1 (4.8%) had an acute, and 3 (14.3%) had resolved infections. The Alinity HCV Ag Next assay demonstrated 99.43% specificity when compared to RNA testing. The Alinity HCV Ag Next assay also detected 91.67% of the active infections compared to RNA testing, while the Elecsys HCV Duo Ag assay detected only 58.33%. The seroconversion panel testing demonstrated that the Alinity HCV Ag Next assay detects an infection within 0.8 days of an RNA result. CONCLUSION: The Alinity HCV Ag Next assay demonstrated excellent concordance to RNA testing in a US urban E.D. POPULATION: This data supports the utility of Alinity HCV Ag Next in diagnosis of active HCV infections.

Kinetics of SARS-CoV-2 Serum Antibodies Through the Alpha, Delta, and Omicron Surges Among Vaccinated Health Care Workers at a Boston Hospital.

Background: Longitudinal serology studies can assist in analyzing the kinetics of antibodies to SARS-CoV-2, helping to inform public health decision making. Our study aims to characterize circulating antibody trends over 18 months in vaccinated participants with and without evidence of COVID-19 infection. Methods: A cohort of health care workers employed at Boston Medical Center was followed to collect serum samples and survey data over 6 time points from July 2020 through December 2021 (N = 527). History of SARS-CoV-2 infection, vaccination, and booster status were confirmed, where possible, through electronic medical records. Serum was assessed for the qualitative and semiquantitative detection of IgG antibody levels (anti-nucleoprotein [anti-N] and anti-spike [anti-S], respectively). Piecewise regression models were utilized to characterize antibody kinetics over time. Results: Anti-S IgG titers remained above the positivity threshold following infection and/or vaccination throughout the 18-month follow-up. Among participants with no evidence of COVID-19 infection, titers declined significantly faster in the initial 90 days after full vaccination (ß = -0.056) from December 2020 to March 2021 as compared with the decline observed following booster dose uptake (ß = -0.023, P < 0.001). Additionally, COVID-19 infection prior to vaccination significantly attenuated the decline of anti-S IgG when compared with no infection following vaccine uptake (P < 0.001). Lastly, fewer participants contracted Omicron when boosted (12.7%) compared to fully vaccinated (17.6%). Regardless of vaccination status, participants who were Omicron positive had lower anti-S IgG titers than those who did not test positive, but this difference was not significant. Conclusions: These findings provide novel 18-month kinetics of anti-S IgG antibodies and highlight the durability of hybrid immunity, underlining the strong humoral response stimulated by combined infection and vaccination.

Reduced Serological Response to COVID-19 Booster Vaccine is Associated with Reduced B Cell Memory in Patients With Inflammatory Bowel Disease; VARIATION [VAriability in Response in IBD AgainsT SARS-COV-2 ImmunisatiON].

BACKGROUND AND AIMS: Patients with inflammatory bowel disease [IBD] have an attenuated response to initial COVID-19 vaccination. We sought to characterize the impact of IBD and its treatment on responses after the third vaccine against SARS-CoV-2. METHODS: This was a prospective multicentre observational study of patients with IBD [n = 202] and healthy controls [HC, n = 92]. Serological response to vaccination was assessed by quantification of anti-spike protein [SP] immunoglobulin [Ig]G levels [anti-SPIgG] and in vitro neutralization of binding to angiotensin-converting enzyme 2 [ACE2]. Peripheral blood B-cell phenotype populations were assessed by flow cytometry. SARS-CoV-2 antigen-specific B-cell responses were assessed in ex vivo culture. RESULTS: Median anti-SP IgG post-third vaccination in our IBD cohort was significantly lower than HCs [7862 vs 19 622 AU/mL, p < 0.001] as was ACE2 binding inhibition [p < 0.001]. IBD patients previously infected with COVID-19 [30%] had similar quantitative antibody response as HCs previously infected with COVID-19 [p = 0.12]. Lowest anti-SP IgG titres and neutralization were seen in IBD patients on anti-tumour necrosis factor [anti-TNF] agents, without prior COVID-19 infection, but all IBD patients show an attenuated vaccine response compared to HCs. Patients with IBD have reduced memory B-cell populations and attenuated B-cell responses to SARS-CoV-2 antigens if not previously infected with COVID-19 [p = 0.01]. Higher anti-TNF drug levels and zinc levels <65 ng/ml were associated with significantly lower serological responses. CONCLUSIONS: Patients with IBD have an attenuated response to three doses of SARS-CoV-2 vaccine. Physicians should consider patients with higher anti-TNF drug levels and/or zinc deficiency as potentially at higher risk of attenuated response to vaccination.

Specificity and Confirmation of SARS-CoV-2 Serological Test Methods in Emergency Department Populations across the United States.

BACKGROUND: Serological testing for SARS-CoV-2 is integral for understanding prevalence of disease, tracking of infections, confirming humoral response to vaccines, and determining timing and efficacy of boosters. The study objective was to compare the specificity of serology assays in emergency department populations across the United States in 2019 (pre-pandemic) and early 2020, incorporating an automated confirmatory assay. METHODS: Patient specimens (n = 1954) were from 4 regions in the United States: New York, NY; Milwaukee, WI; Miami, FL; and Los Angeles, CA. Specimens were tested with SARS-CoV-2 anti-spike receptor-binding domain assays: SARS-CoV-2 IgG on the Abbott Alinity i (AdviseDx SARS-Cov-2 IgG II) and Beckman Coulter Access 2 (SARS-CoV-2 IgG II), and SARS-CoV-2 IgM on the Abbott Alinity i (AdviseDx SARS-CoV-2 IgM). Reactive samples were tested with a research use only angiotensin-converting enzyme 2 binding inhibition assay (Abbott ARCHITECT) for confirmation of SARS-CoV-2 neutralizing antibodies. Assay specificity was determined and comparisons performed with Fisher's exact test. RESULTS: Overall SARS-CoV-2 IgG specificity was 99.28% (95% confidence interval, 98.80%-99.61%), 99.39% (98.93%-99.68%), and 99.44% (98.99%-99.72%) for SARS-CoV-2 IgG by Abbott and Beckman, and SARS-CoV-2 IgM, respectively. Overall agreement for the two IgG assays was 99.28% (range for the 4 sites: 98.21% to 100%). There were no specificity differences between assays or sites. CONCLUSIONS: The specificity of the serological assays evaluated in a large, diverse emergency department population was >99% and did not vary by geographical site. A confirmatory algorithm with an automated pseudo-neutralization assay allowed testing on the same specimen while reducing the false positivity rate and increasing the value of serology screening methods.

Specificity and Confirmation of SARS-CoV-2 Serological Test Methods in Emergency Department Populations Across the United States in 2019 and Early 2020.

BACKGROUND: Serological testing for SARS-CoV-2 is integral for understanding prevalence of disease, tracking of infections, confirming humoral response to vaccines, and determining timing and efficacy of boosters. The study objective was to compare the specificity of serology assays in emergency department populations across the United States in 2019 (pre-pandemic) early 2020 incorporating an automated confirmatory assay. METHODS: Patient specimens (n = 1954) were from four regions in the United States: New York, NY; Milwaukee, WI; Miami, FL; and Los Angeles, CA. Specimens were tested with SARS-CoV-2 anti-spike receptor binding domain assays: SARS-CoV-2 IgG on the Abbott Alinity i (AdviseDx SARS-Cov-2 IgG II) and Beckman Coulter Access 2 (SARS-CoV-2 IgG II), and SARS-CoV-2 IgM on the Abbott Alinity i (AdviseDx SARS-CoV-2 IgM). Reactive samples were tested with a research use only ACE2 binding inhibition assay (Abbott ARCHITECT) for confirmation of SARS-CoV-2 neutralizing antibodies. Assay specificity was determined and comparisons performed with Fisher's Exact Test. RESULTS: Overall SARS-CoV-2 IgG specificity was 99.28% (95% confidence interval: 98.80%-99.61%), 99.39% (98.93%-99.68%), and 99.44% (98.99%-99.72%) for SARS-CoV-2 IgG by Abbott and Beckman, and SARS-CoV-2 IgM, respectively. Overall agreement for the two IgG assays was 99.28% (range for the four sites: 98.21%-100%). There were no specificity differences between assays or sites. CONCLUSIONS: The specificity of the serological assays evaluated in a large diverse emergency department population was >99% and did not vary by geographical site. A confirmatory algorithm with an automated pseudo-neutralization assay allowed testing on the same specimen while reducing the false positivity rate and increasing the value of serology screening methods.

SARS-CoV-2 Anti-Spike IgG Antibody and ACE2 Receptor Binding Inhibition Levels among Breakthrough Stage Veteran Patients.

SARS-CoV-2 mRNA vaccines have been critical to curbing pandemic COVID-19; however, a major shortcoming has been the inability to assess levels of protection after vaccination. This study assessed serologic status of breakthrough infections in vaccinated patients at a Veterans Administration medical center from June through December 2021 during a SARS-CoV-2 delta variant wave. Breakthrough occurred mostly beyond 150 days after two-dose vaccination with a mean of 239 days. Anti-SARS-CoV-2 spike (S) IgG levels were low at 0 to 2 days postsymptoms but increased in subjects presenting thereafter. Population measurements of anti-S IgG and angiotensin converting enzyme-2 receptor (ACE2-R) binding inhibition among uninfected, vaccinated patients suggested immune decay occurred after 150 days with 62% having anti-S IgG levels at or below 1,000 AU comparable with breakthrough patients at 0 to 2 days postsymptom onset. In contrast, vaccination after resolved infection conferred robust enduring anti-S IgG levels (5,000 to >50,000 AU) with >90% ACE2-R binding inhibition. However, monoclonal antibody (MAb)-treated patients did not benefit from their prior infection suggesting impaired establishment of B cell memory. Analysis of boosted patients confirmed the benefit of a third vaccine dose with most having anti-S IgG levels above 5,000 AU with >90% ACE2-R binding inhibition, but a subset had levels <5,000 AU. Anti-S IgG levels >5,000 AU were associated with >90% ACE2-R binding inhibition and no documented breakthrough infections, whereas levels falling below 5,000 AU and approaching 1,000 AU were associated with breakthrough infections. Thus, quantitative antibody measurements may provide a means to guide vaccination intervals for the individual. IMPORTANCE Currently, clinicians have no guidance for the serologic assessment of SARS-Cov-2 postvaccination status regarding protection and risk of infection. Vaccination and boosters are administered blindly without evaluation of need or outcome at the individual level. The recent development of automated quantitative assays for anti-SARS-CoV-2 spike protein IgG antibodies permits accurate measurement of humoral immunity in standardized units. Clinical studies, such as reported here, will help establish protective antibody levels allowing identification and targeted management of poor vaccine responders and vaccinated subjects undergoing immune decay.

Reduced Serological Response to COVID-19 Vaccines in Patients with IBD is Further Diminished by TNF Inhibitor Therapy; Early Results of the VARIATION study [VAriability in Response in IBD Against SARS-COV-2 ImmunisatiON].

BACKGROUND AND AIMS: Evidence suggests patients with inflammatory bowel disease [IBD] receiving TNF antagonists have attenuated response to vaccination against COVID-19. We sought to determine the impact of IBD and of various medications for treatment of IBD on antibody responses to vaccination against COVID-19. METHODS: Patients with IBD [n = 270] and healthy controls [HC, n = 116] were recruited prospectively, and quantitative antibody responses were assessed following COVID-19 vaccination. The impact of IBD and of medications for treatment of IBD on vaccine response rates was investigated. RESULTS: Of HC, 100% seroconverted following complete vaccination with two vaccine doses; 2% of patients with IBD failed to seroconvert. Median anti-spike protein [SP] immunoglobulin [Ig]G levels following complete vaccination in our IBD cohort was significantly lower than among HC [2613 AU/mL versus 6871 AU/mL, p ≤0.001]. A diagnosis of IBD was independently associated with lower anti-SP IgG levels [ß coefficient -0.2, p = 0.001]. Use of mRNA vaccines was independently associated with higher anti-SP IgG levels [ß coefficient 0.25, p ≤0.001]. Patients with IBD receiving TNF inhibitors had significantly lower anti-SP IgG levels [2445 AU/mL] than IBD patients not receiving TNF inhibitors [3868 AU/mL, p ≤0.001]. Patients with IBD not receiving TNF inhibitors still showed attenuated responses compared with HC [3868 AU/mL versus 8747 AU/mL, p = 0.001]. CONCLUSIONS: Patients with IBD have attenuated serological responses to SARS-CoV-2 vaccination. Use of anti-TNF therapy negatively affects anti-SP IgG levels further. Patients who do not seroconvert following vaccination are a particularly vulnerable cohort. Impaired responses to vaccination in our study highlight the importance of booster vaccination programmes for patients with IBD.

Time-related performance characteristics of high-sensitivity troponin I assay using manufacturer's controls and reagents.

BACKGROUND: Troponin is a widely used cardiac protein biomarker for acute coronary syndrome. Its increasing importance drives an increasing need to assess, in real-world conditions, the performance of the tests to measure it. We evaluated the performance characteristics of high-sensitivity troponin I assay reagents and ancillary agents on the Abbott ARCHITECT ci4100, ARCHITECT i2000SR and Alinity ci using historical quality control data spanning 5 years. DESIGN AND METHOD: Retrospective diagnostic hs-TnI quality control data were collected between 2015 and 2019 from the Abbott ARCHITECT ci4100, ARCHITECT i2000SR and Alinity ci located in the University College Dublin Clinical Research Centre Core Lab facility. Descriptive statistics for bias and variability were generated. Linear regression models were used to calculate the mean hs-TnI concentrations over Abbott quality control or reagent lot age and over time from the last calibration of the analysers. RESULTS: Measurement bias on all three systems ranged between -2.49% and 3.98%. The total CV was ≤8.80%, with a within-lot variability for the reagents and controls of ≤5.45% and ≤7.13%, respectively. The between-lot CVs for reagents and controls were ≤7.16% and 6.19%, respectively. The effect of control or reagent age did not greatly affect stability over time. Results were also stable over different times from the last calibration of the analysers. CONCLUSION: The results of this study show that the Abbott hs-TnI assay on the ARCHITECT i2000sr and ARCHITECT ci4000 systems is quite stable in a core laboratory environment. The Alinity ci system exhibits similar performance characteristics.

Anti-SARS-CoV-2 IgM improves clinical sensitivity early in disease course.

INTRODUCTION: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is diagnosed by molecular-based detection of SARS-CoV-2 RNA. Serologic testing detects antibodies specific to SARS-CoV-2 and IgM specifically may serve as an adjunct test to PCR early in disease. We evaluated the Abbott anti-SARS-CoV-2 IgM and IgG assays along with DiaSorin anti-SARS-CoV-2 IgG and Roche anti-SARS-CoV-2 Total. METHODS: Specimens from 175 PCR-positive patients and 107 control specimens were analyzed using Abbott IgM and IgG, DiaSorin IgG, and Roche Total (IgA, IgG, IgM) assays. Sensitivity, specificity, cross-reactivity, concordance between assays, trends over time, positive predictive value (PPV), and negative predictive value (NPV) were determined. RESULTS: Abbott IgM sensitivity was 63.6% at 0 days post-PCR positivity, 76.5% at 1-5d, 76.3% at 6-14d, 85.2% at 15-30d, and 63.6% at > 30d. All assays exhibited highest sensitivity 15-30d post-PCR positivity (83.3-85.2%). Combining Abbott IgM and IgG improved sensitivity by 22.7% compared to IgG alone when tested 0d post-PCR positivity. All assays had a specificity of 100% and only Abbott IgG exhibited cross-reactivity (anti-dsDNA). Cohen's kappa varied between 0.86 and 0.93. Time to seroconversion from PCR positivity was lowest for Abbott IgM and highest for Abbott IgG. NPV was highest for Abbott IgM < 14 days post-PCR positivity and Abbott IgG ≥ 14 days. CONCLUSION: The Abbott IgM assay exhibited the earliest response and greatest signal in most patients evaluated for serial sampling and had the highest NPV < 14 days post-PCR positivity, suggesting its potential utility as an adjunct test to PCR early in disease course.

Performance characteristics of the high sensitivity Alinity i & ARCHITECT HBsAg Next Qualitative/Confirmatory assays.

Despite improvement in vaccinations, Hepatitis B remains a major health concern due to the difficulty of prevention even in low endemic areas such as Europe. In this report we describe the performance characteristics of the new HBsAg Next Qualitative and HBsAg Next Confirmatory assays designed for blood screening and diagnostic purposes on the Alinity i and ARCHITECT fully automated systems. The new assays were evaluated in comparison to the ARCHITECT HBsAg Qualitative II and Confirmatory assays on seroconversion, analytical sensitivity, and mutant panels along with testing of over 400 clinical positive samples demonstrating excellent improvements in sensitivity. Additionally, specificity was shown to be improved with testing of over 6000 donors and 240 diagnostic specimens. Overall, the Alinity i & ARCHITECT HBsAg Next assays have taken a step forward in improving the detection of Hepatitis B virus.

A novel Sigma metric encompasses global multi-site performance of 18 assays on the Abbott Alinity system.

OBJECTIVES: The Abbott Alinity family of chemistry and immunoassay systems recently launched with early adopters contributing imprecision and bias data, which was consolidated to assess the performance of Alinity assays across multiple sites using the Sigma metric. Multi-site Sigma metrics were determined for 3 ion-selective electrodes, 12 photometric assays, and 3 immunoassays across 11 independent laboratory sites in 9 countries. METHODS: Total allowable error (TEa) goals followed a previously defined hierarchy that used CLIA as the primary goal. Bias was calculated against the Abbott ARCHITECT system using Passing-Bablok regression analysis using individual site data or pooled aggregate data. Sigma metrics were calculated as (%TEa - |% bias|)/%CV. For individual-site analysis, the Sigma metrics for each assay were compared using the individual-site and the pooled biases. For multi-site analysis, the average CV and the pooled bias were used to generate a Pooled Sigma metric encompassing the global performance for a given assay. RESULTS: A total of 97 individual-site and 18 Pooled Sigma metrics were calculated for available assays. Individual Sigma metrics varied across sites, with 90% of assays performing 4 Sigma or higher, and 17 of 18 Pooled Sigma metrics indicated performance greater than 4 Sigma. Sigma metrics were significantly improved in 16 assays when using pooled bias rather than individual-site bias. CONCLUSIONS: This multi-center study applies a novel application of Sigma metrics to the first Alinity users and reveals analytical performance of greater than 4 Sigma for vast majority of assays. Laboratories with limited resources can leverage larger data sets for Pooled Sigma metric analysis, providing a tool to assess the consistency of analytical performance from multiple sites.

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.

Multicenter evaluation of a new, automated enzyme-linked immunoassay for detection of human immunodeficiency virus-specific antibodies and antigen.

A collaborative multicenter study was conducted to evaluate the sensitivity, specificity, and precision of a three-step, fully automated, qualitative microparticle-based enzyme-linked immunoassay (AxSYM HIV Ag/Ab Combo; Abbott Laboratories), designed to simultaneously detect (i). antibodies against human immunodeficiency virus type 1 (HIV-1) and/or type 2 (HIV-2) and (ii). HIV p24 antigen. A significant reduction in the HIV seroconversion window was achieved by combining detection of HIV antibodies and antigen into a single assay format. For 22 selected, commercial HIV seroconversion panels, the mean time of detection with the combined-format HIV antigen-antibody assay was reduced by 6.15 days compared to that with a similar third-generation single-format HIV antibody assay. The quantitative sensitivity of the combination assay for the p24 antigen (17.5 pg/ml by use of the p24 quantitative panel VIH SFTS96') was nearly equivalent to that of single-format antigen tests. The combination assay demonstrated sensitive (100%) detection of anti-HIV immunoglobulin in specimens from individuals in CDC stages A, B, and C and from individuals infected with different HIV-1 group M subtypes, group O, or HIV-2. The apparent specificity for hospitalized patients (n = 1938) was 99.90%. In a random population of 7900 volunteer blood donors, the specificity (99.87%) was comparable to that of a third-generation single-format HIV antibody assay (99.92%) on the same donor specimens. In addition, the combination assay was robust to potential interfering specimens. The precision of the combination was high, with intra- and interrun variances of