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.

Improved detection of early acute, late acute, and occult Hepatitis B infections by an increased sensitivity HBsAg assay.

BACKGROUND: Hepatitis B surface antigen (HBsAg) is the primary marker for diagnosis of acute and chronic hepatitis B. Although HBsAg assays have undergone continuous improvement, gaps remain in the detection of early and late acute infection and occult hepatitis B infection (OBI). OBJECTIVES: The performance of a prototype, improved sensitivity HBsAg assay run on the ARCHITECT and Alinity instruments was evaluated for detection of early and late acute infection and OBI. STUDY DESIGN: Seventy seven early acute samples [positive only for hepatitis B viral DNA (HBV DNA)], twelve seroconversion panels spanning late acute infection, and 101 occult samples (HBsAg negative, positive for HBV DNA and anti-HBc) were tested with the prototype assay and ARCHITECT HBsAg Qualitative II. HBsAg gene sequencing was performed to determine genotype and mutations in the immunodominant region. RESULTS: Compared with ARCHITECT HBsAg Qualitative II, the prototype assay showed increased detection of NAT yield samples (28/77, 36.4%,), late acute samples (≥13 days longer detection of HBsAg for 6/12 panels), and OBI samples (11/101, 10.9%). HBsAg sequence data were obtained for 62 samples. Genotypes represented were A1, A2, B2, B4, C1, C2, C5, D3, E, and H. HBsAg escape mutations were found in 4.8% of NAT yield and 38.9% of OBI samples sequenced. Prototype assay values for 188 samples were equivalent on the ARCHITECT and Alinity instruments. CONCLUSIONS: The new prototype HBsAg assay will be of diagnostic value in providing improved detection of early acute, late acute, and occult HBV infections.

Comparative evaluation of the new ARCHITECT EBV assays considering different testing algorithms.

In the current evaluation, Epstein-Barr virus (EBV) serology was performed on 1113 routine serum samples. Although the initial request for all samples from the general practitioner was EBV IgM testing, 80.9% were classified as past infections. The ARCHITECT(®) viral capsid antigen (VCA) IgM, VCA IgG, and EBV nuclear antigen (EBNA) 1 IgG assays showed good results for sensitivity and specificity, being 100.0%, 98.3%, and 100.0% and 99.9%, 95.4%, and 99.6%, respectively. Using an algorithm based on initial EBNA-1 IgG testing, followed by VCA IgG and IgM for samples that were not EBNA-1 IgG reactive, the number of tests per sample could be reduced to nearly 50% compared to parallel testing. The high sensitivity and specificity of the ARCHITECT(®) EBNA-1 IgG assay in combination with a low number of grayzone results are a precondition for the chosen test algorithm. Thus, the newly developed ARCHITECT(®) EBV panel is suitable for accurate and cost-efficient EBV serology in a routine clinical laboratory.

Evaluation of the Abbott ARCHITECT Chagas prototype assay.

Serologic tests are established tools for the diagnosis of Chagas disease applied to support a safe blood supply in endemic countries. However, sensitivity and specificity of most commercially available enzyme-linked immunosorbent assays (ELISAs) are not regarded as adequate enough to rely on a single assay to determine the Trypanosoma cruzi infection status of a blood donor or a patient. The overall assay performance is driven by the general choice of antigens and the actual antigen cocktail provided in the test. In this report we describe key performance data of the Abbott ARCHITECT Chagas prototype assay in comparison to the well-recognized bioMérieux ELISA cruzi assay. The ARCHITECT assay demonstrated superior specificity (99.99% versus 99.93%) and sensitivity (99.85% versus 98.38%), along with excellent precision, thus showing the potential to serve as single assay to determine the T. cruzi status of a given blood unit or diagnostic specimen on a fully automated instrument platform.

Comparative evaluation of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays for anti-Toxoplasma antibodies detection in pregnant women sera.

We assessed the performance of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays against corresponding assays on AxSYM and Vidas using 730 sera from pregnant women. The ARCHITECT Toxo IgG and IgM assays showed a relative sensitivity of 97.5% and 89.9% and a relative specificity of 99.1% and 99.8%, respectively. If IgM sensitivity is calculated only for sera drawn less than 4 months after infection, the relative sensitivity rises to 98.1%. Correlation between the ARCHITECT and Vidas Avidity assays was 0.87 (n = 103). Testing 86 IgG-positive specimens from recent infection (<4 months), we never obtained high avidity results, but 2 specimens were in the gray zone, whereas sera from past infections (>4 months) exhibited high avidity results in 72.5% (137/189) of cases. The method can be used reliably to exclude recent infections in sera with concurrently positive results for IgM and IgG (IgG, >3 IU/mL).

Evaluation of the Abbott ARCHITECT Toxo IgM assay.

Development of the ARCHITECT Toxo IgM assay has been done to assist the clinician in acute Toxoplasma gondii infection detection, especially in pregnant women. Its use, in conjunction with ARCHITECT Toxo IgG and Toxo Avidity assays, will provide an array of assays particularly useful in the monitoring of pregnant females to determine the risk of maternal transmission of the parasite. Specificity results from 2 testing sites, using populations of pregnant females, hospital patients, and blood donors, demonstrated that the assay has an overall resolved relative specificity of 99.89% (confidence interval, 99.68-99.98%). Relative specificity for pregnant female specimens was 99.95% (n = 2031). Excellent seroconversion sensitivity was observed for the ARCHITECT Toxo IgM assay, which was similar to the Abbott AxSYM Toxo IgM assay (Abbott Laboratories, Abbott Park, IL). In more than 90% of the panels tested, the 1st bleed detected in the serial bleeds was the same for both assays.

Development of fully automated determination of marker-specific immunoglobulin G (IgG) avidity based on the avidity competition assay format: application for Abbott Architect cytomegalovirus and Toxo IgG Avidity assays.

Determination of the avidity of immunoglobulin G (IgG) directed against a specific marker has become an established diagnostic tool for identifying or excluding acute infections with pathogens. A novel assay format termed AVIcomp (avidity competition based on mass action) circumventing the conventional chaotropic format has been developed for determination of the avidity of marker-specific IgG in patient specimens. Its applications for cytomegalovirus (CMV) and Toxoplasma gondii are presented. Specific high-avidity IgG from the patient specimen is selectively blocked using a soluble antigen in a sample pretreatment reagent, and the amount of remaining specific low-avidity IgG is determined relative to that in an untreated control. The comparison of the conventional chaotropic format, represented by the Radim CMV IgG Avidity assay, and the newly developed AVIcomp method, as exemplified by the Architect CMV IgG Avidity assay, on blood drawn within 4 months after seroconversion revealed a sensitivity of 100% (97.3% by an alternative calculation) for the AVIcomp format versus 87.5% (75.7% by an alternative calculation) for the chaotropic avidity assay. The specificity on 312 CMV IgG reactive and CMV IgM nonreactive specimens from pregnant women was 100% for the AVIcomp assay and 99.7% for the conventional avidity assay. The Architect Toxo IgG Avidity assay showed an agreement of 97.2% with the bioMérieux Vidas Toxo IgG Avidity Assay employing chaotropic reagents. These performance data suggest that the AVIcomp format shows superior sensitivity and equivalent specificity for the determination of IgG avidity to assays based on the chaotropic method and that the AVIcomp format may also be applicable to other disease states.

Performance characteristics of the new ARCHITECT Toxo IgG and Toxo IgG Avidity assays.

The ARCHITECT Toxo IgG and IgG Avidity assays have been developed as a fully automated panel for immune status determination and acute infection exclusion. Resolved relative specificity and sensitivity of the ARCHITECT Toxo IgG assay were 99.6% (1359/1365) and 99.7% (1096/1099) as determined on pregnant females, blood donor, and diagnostic specimens. Seroconversion sensitivity of the ARCHITECT assay was comparable with the AxSYM Toxo IgG assay. The ARCHITECT Toxo IgG Avidity assay detected 100.0% (124/124) of acute phase specimens (<4 months after infection) as low avidity, whereas the Vidas Toxo IgG Avidity assay detected 98.9% (89/90) as low avidity. In summary, the ARCHITECT Toxo IgG assay, using recombinant antigens, showed excellent specificity and sensitivity for acute phase as well as past infection specimens. The ARCHITECT Toxoplasmosis panel can be reliably used to rule out acute Toxoplasma gondii infection in pregnant women.

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

BACKGROUND: Before the introduction of human immunodeficiency virus (HIV) combination assays, serologic diagnosis of HIV infection was performed with assays that detected either antibodies or p24 antigen. Owing to the capability to detect the early appearance of p24 antigen, combination assays that are designed for simultaneous detection of antibodies and antigen can significantly reduce the diagnostic window. STUDY DESIGN AND METHODS: Specificity and sensitivity of a commercially available HIV antigen-antibody combination assay (Abbott PRISM; assay is not licensed by the FDA for use in the United States) were evaluated in a multicenter study by testing volunteer blood donors, hospitalized patients, seroconversion panels, and p24 antigen and HIV antibody subtype panels. Performance data were compared to a commercially available HIV combination assay and the PRISM HIV O Plus assay. RESULTS: Apparent specificity of 99.95 percent was observed in the donor population for the PRISM HIV antigen-antibody combination assay, and better seroconversion sensitivity was demonstrated compared with another combination assay and the PRISM HIV O Plus assay. Analytical HIV antigen detection sensitivity averaged 33 pg per mL on the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSAPS) panel. Furthermore, comparable antigen sensitivity was demonstrated for 32 HIV-1 group M subtype and group O panels. The PRISM HIV combination assay detected all HIV-1 group M and O and HIV-2 antibody-positive specimens evaluated. CONCLUSIONS: The PRISM HIV antigen-antibody combination assay demonstrated a significant reduction of the window period for diagnosis of HIV infection. The assay demonstrated enhanced specificity and sensitivity along with broad subtype detection. The assay performance represents the "state-of-the art" technology for serologic blood screening of HIV infection.

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