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

FATIN FARAHAH BINTI HASAM

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28.03.2023

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INTRODUCTION

MATERIAL & METHODS

RESULTS

DISCUSSION

INTRODUCTION

• Although vaccination programs for Hepatitis B have been available since 1982 (WHO Hepatitis B key facts, 2019), viral hepatitis is still one of the 10 main causes of death, with Hepatitis B and C causing 96% of all hepatitis mortality (Global Hepatitis Report, 2017)
• Hepatitis B surface antigen (HBsAg) is the first and most important antigenic marker for early and late acute as well as chronic infection detection (Kuhns et al., 2019a; Yang et al., 2016).
• Although assays for HBsAg detection have been constantly improved (Enjalbert et al., 2014; Mortensen et al., 2016; Candotti and Laperche, 2018; Gerlich et al., 2018), there is still a need for higher sensitivity assays, to avoid false negatives in the diagnostic as well as transfusion settings, due to escape mutants, new genotypes, reactivation and occult infection.

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INTRODUCTION

• NAT testing is more sensitive but also brings with it higher costs and the need for specialized equipment/facilities that are frequently prohibitive in developing countries.
• Therefore, sensitive HBsAg assays approaching minipool NAT sensitivity (Lou et al., 2018) could be an alternative especially in developing countries due to cost-effectiveness or in low prevalence areas.

INTRODUCTION

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 random-access analyzers in comparison to the current on-market ARCHITECT HBsAg Qualitative II/ Confirmatory assay

2. Materials and methods

TESTING SITES

Testing was performed at one external site, i.e. Sanquin National Screening Laboratory, Amsterdam, Netherlands and internally at the research laboratories of Abbott GmbH, in Wiesbaden, Germany

ASSAY PRINCIPLE

The HBsAg Next assay is a one-step chemiluminescent microparticle immunoassay (CMIA) assay that has been built to run on both the Abbott Alinity i and the ARCHITECT i Systems.

The Abbott ARCHITECT i analyzer system is the predecessor of the Alinity i system. The assay detects the qualitative presence of HBsAg and is calibrated/ traceable to the World Health Organization (WHO) Second International Standard for HBsAg (subtype adw2, genotype A, NIBSC Code 00/ 588).

Specimens and Testing procedures

Seroconversion sensitivity

Seroconversion sensitivity was evaluated on a panel consisting of consecutive bleeds from 32 seroconverting donors obtained from commercial vendors. Testing was performed on Alinity i HBsAg Next Qualitative and ARCHITECT HBsAg Qualitative II.

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Analytical sensitivity

Analytical Sensitivity of the ARCHITECT and Alinity i HBsAg Next Qualitative and Confirmatory assays was evaluated on the 2nd and 3rd WHO International standards for HBsAg, subtype adw2, genotype A, NIBSC code: 00/588 and NIBSC code 12/226, respectively.

Specimens and Testing procedures

Clinical sensitivity

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Clinical sensitivity was evaluated, by testing 450 samples known to be HBsAg positive and HBV NAT positive from acute (n = 12) and chronic (n = 94) phases of infection as well as from undefined infection stage (n = 344), all sourced from a variety of commercial suppliers. Testing was performed on ARCHITECT and Alinity i HBsAg Next Qualitative and Confirmatory compared to ARCHITECT HBsAg Qualitative II and Confirmatory. However, testing could not be completed for all specimens on Alinity i HBsAg Next due to sample depletion (total n=444).

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Mutant panel

Further sensitivity testing was completed on a total of 167 mutant panel specimens consisting of 71 recombinant mutant samples, 2 wild type controls and 94 native mutant samples collected through Abbott’s Global Viral Surveillance Program (Harris et al., 2017; Rodgers et al., 2017).

Specimens and Testing procedures

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Clinical specificity

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Clinical specificity of the ARCHITECT HBsAg Next Qualitative assay in a blood bank population was evaluated on 6618 donor specimens (collected in 3300 serum and 3318 plasma tubes) in comparison to ARCHITECT HBsAg Qualitative II. The Alinity i HBsAg assay was evaluated in a separate study using 6718 donor specimens (collected in 3181 serum and in 3537 plasma tubes).

Clinical specificity in a diagnostic setting was evaluated on a population of 240 serum and plasma specimens from hospitalized patients obtained from a commercial supplier

Within assay sample carryover

Within sample carryover was evaluated by testing a high positive specimen at a concentration ≥125,000 IU/mL followed by a high negative specimen testing at ~0.76 S/CO. The testing was carried out for 10 iterations.

RESULTS

• In 25 of 32 panels (78%) the number of days to the first repeat re?active and confirmed result was less for Alinity i HBsAg Next Qualita?tive compared to ARCHITECT HBsAg Qualitative II. For the remaining 7 panels, the investigational and comparator assay showed no differ?ence in the number of days to the first repeatedly reactive and confirmed resul

SEROCONVERSION SENSITIVITY

• For Alinity i and ARCHITECT HBsAg Next Qualitative analytical sensitivity values of 4.50 to 5.97 mIU/mL and 4.62 to 6.14 mIU/mL, respec?tively, have been obtained when using the WHO 2nd International Standard across reagent lots.
• The Alinity i and ARCHITECT HBsAg Next Qualitative assays were about 4-fold more sensitive compared to ARCHITECT HBsAg Qualitative II with an analytical sensitivity of 17.00 to 22.00 mIU/mL across reagent lots

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ANALYTICAL SENSITIVITY

• The clinical sensitivity was determined to be 100.00% for both investigational Alinity i and ARCHITECT HBsAg Next Qualitative assays for the three sample categories tested.
• In comparison, the ARCHITECT HBsAg Qualitative II assay achieved an overall sensitivity of 99.78% (Table 1)

CLINICAL SENSITIVITY

TABLE 1

RESULTS

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• S/CO results of more than 100 were observed for single panel members that were detected at about 2 S/CO in the comparator assay with an on average 7-fold increase in S/CO values over the ARCHITECT HBsAg Qualitative II assay
• The new HBsAg Next Confirmatory assay showed a more efficient neutralization of mutant specimens as compared to the respective ARCHITECT HBsAg Qualitative II confirmatory assay

MUTANTS

RESULTS

• The ARCHITECT and Alinity i HBsAg Next Qualitative assays were assessed to have comparable specificity of 99.95% and 99.96%, respectively, on blood donations, and both 100% specificity on a diagnostic population.
• The predecessor assay ARCHITECT HBsAg Qualitative II showed a slightly lower specificity of 99.92% on blood donors, but also 100% on diagnostic specimens

CLINICAL SPECIFICITY ON BLOOD DONORS AND DIAGNOSTIC SPECIMENS

RESULTS

• The difference between the protected sample (nonreactive specimen not exposed to replicates of the positive sample prior to testing) and the unprotected sample (run immediately after an extremely high positive HBsAg specimen) had an absolute bias of 0.08 S/CO (confidence interval: 0.02 to 0.13) for a high nonreactive sample running at 0.76 S/CO

WITHIN ASSAY SAMPLE CARRYOVER

DISCUSSION

• The new HBsAg Next assays on the Alinity i / ARCHITECT was increased about 4-fold compared to the on market already very sensitive ARCHITECT HBsAg
• The increased analytical sensitivity enables better clinical diagnostic and screening sensitivity, mutant detection and seroconversion sensitivity.

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DISCUSSION

• Overall, the Alinity i/ ARCHITECT HBsAg Next Qualitative assays showed significantly improved sensitivity compared to the ARCHITECT HBsAg Qualitative II assay without compromising specificity.
• The parallel improvement of sensitivity and neutralization capacity of the Alinity i and ARCHITECT HBsAg Next Confirmatory assays allows laboratories the use of common reagents without having to rely on alternate methods (e.g. PCR) to confirm HBsAg positive specimens.
• The improved sensitivity of the HBsAg Next Qualitative / Confirmatory assays significantly improves detection and confirmation of HBsAg early and late infection.

Thank You