Determination of a Positive Predictive Value for Confirming HBsAg Qualitative II on Architect and Alinity i (Abbott Diagnostics).

Background: Hepatitis B surface antigen (HBsAg) is an early and sensitive serum marker of infectivity for the detection of hepatitis B virus (HBV) infection. The availability of sensitive methods for its detection can generate false-positive results, requiring a confirmatory test that is both costly and unavailable in all medical laboratories. The objective of the study was to determine, using the two automated systems (Architect and Alinity i (Abbott)), a cutoff value at which HBsAg is considered positive without the need for a confirmatory test and to assess the role of anti-HBc antibodies as an indirect marker of qualitative HBsAg confirmation.

Methods: The study included 328 HBsAg positive (≥ 1 S/CO) and repeatable samples tested on Architect (Abbott) or Alinity i (Abbott) using the microparticle chemiluminescence immunoassay technique (CMIA). The samples were confirmed by the Architect or Alinity i HBs Ag qualitative II Confirmatory neutralization test, with concomitant detection of anti-HBc antibodies in the majority of patients.

Results: Out of the 223 repeatably reactive samples tested on Architect, 173 (77.6%) were true positives and 50 (22.42%) were false positives. For samples processed on Alinity i, out of the 131 tested, 105 (78.9%) were true positives and 26 (21.1%) were false positives. A specificity of 100% was obtained, with an HBsAg index value of 14.04 for Architect and 24.93 for Alinity i. Regarding the results of the anti-HBc total antibodies assay, they were concordant with the results of the confirmatory test in 89.62% and 95.03% for Architect (Abbott) and Alinity i (Abbott), respectively.

Conclusions: Our study showed concordance between the Architect and Alinity i (Abbott) automated systems. According to ROC curve, the neutralization test is particularly relevant for HBsAg index values between 1.15 S/CO and 24.93 S/CO. Using Architect (Abbott), anti-HBc antibody test diagnosed 89.62% of cases, while Alinity (Abbott) achieved over 95%.