ARCHITECT HBsAg Next assay is positioned better to resolve and refine challenging weak reactive clinical samples

Ultrasensitive HBsAg assays are replacing the previous versions. Unlike the sensitivity, the specificity, and its positioning to resolve weak-reactives (WR) are not studied. We investigated the ability of ARCHITECT HBsAg-Next (HBsAg-Nx) assay to resolve WR and sought its clinical validation and correlation with confirmatory/reflex testing.

Among 99,761 samples between Jan 2022 - 2023, 248 reactive samples in HBsAg-Qual-II were compared with HBsAg-Nx assay. Sufficient samples were further subjected to neutralization (n = 108) and reflex (anti-HBc total/anti-HBs antibody) testing.

Out of 248 initial reactive samples in HBsAg-Qual-II, 180 (72.58%) were repeat reactive, and 68 (27.42%) were negative, whereas in HBsAg-Nx, 89 (35.89%) were reactive and 159 (64.11%) were negative (p<0.0001). Comparing the results of two assays (Qual-II/Next), 57.67% (n = 143) were concordant (++/-) and 105 (42.33%) were discordant (p = 0.0025). Testing of HBsAg-Qual-II ⁺ & HBsAg-Nx ^- samples revealed that 85.71% (n = 90) were anti-HBc total negative and 98.08% (n = 51) were not neutralized as well as significant proportion (89%) had no clinical correlation. The proportion of samples neutralized was significantly different between ≤5 S/Co (26.59%) and >5 S/Co (71.42%) (p = 0.0002). All samples (n = 26) with enhanced reactivity in HBsAg-Nx were effectively neutralized, while samples with no increase in reactivity, 89% (n = 72) failed neutralization (p=<0.001).

HBsAg-Nx assay is positioned better to resolve and refine challenging WR samples than Qual-II which correlated well with confirmatory/reflex tests and clinical disease. This superior internal benchmarking significantly reduced the cost and quantum of retesting, confirmatory/reflex testing in the diagnosis of HBV infection.