Elecsys® HBsAg II

Immunoassay for the qualitative determination of hepatitis B surface antigen (HBsAg)

Elecsys HBsAg II

Immunoassay for the qualitative determination of hepatitis B surface antigen (HBsAg)

Hepatitis B is a potentially life threatening liver infection caused by the hepatitis B virus (HBV). It is transmitted through contact with the blood or other body fluids of an infected person.1

The disease is not always self limiting: In adults approx. 5 % of acute infections will follow a chronic course of varying degrees of severity; infants will develop chronic hepatitis B in up to 90 % of the cases.1 An estimated 257 million people are living with HBV infection. In 2015, hepatitis B resulted in 887,000 deaths, mostly from complications (including cirrhosis and hepatocellular carcinoma).1 Hepatitis B surface antigen (HBsAg) is a polypeptide component of the external envelope of HBV, presenting various immunogenic determinants.2

After infection, HBsAg is the first immunologic marker detectable in serum and is usually present weeks before the onset of clinical symptoms and the appearance of other biochemical markers.3 HBsAg assays are used within the scope of diagnostic procedures to identify persons infected with HBV and prevent the transmission of the virus by blood and blood products.1

Under selective pressure HBV may mutate, potentially leading to escape from a host’s protection after vaccination and undetectability with certain commercially available HBsAg assays.4 The Elecsys® HBsAg II assay was specifically designed to detect a multitude of such mutants. 

Most relevant HBsAg mutations - need to be detected by state-of-the-art HBsAg assays5,6

  • Most relevant mutations in the a-determinant of the HBsAg
    • substitutions G145R, K141E, T131I
    • insertions between amino acids 122/123
  • In addition, mutations near the a-determinant or in regulatory elements of the surface gene may also affect the antigenic structure
Elecsys HBsAg II

Elecsys® HBsAg II

  • Systems

    cobas e 411 analyzer, cobas e 601 / cobas e 602 modules, cobas e 801 module

  • Testing Time

    18 minutes

  • Test principle

    One-step double antigen sandwich assay.

  • Calibration


  • Interpretation

    COI <0.9 = non-reactive 
    COI ≥0.9 – <1.0 = gray zone 
    COI ≥1.0 = reactive

  • Sample material

    Serum collected using standard sampling tubes or tubes containing separating gel. Li‑heparin, Na‑heparin, K2‑EDTA, K3‑EDTA, ACD, CPD, CP2D, CPDA and Na‑citrate plasma. Plasma tubes containing separating gel can be used.

  • Sample volume

    50 μL cobas e 411 analyzer, cobas e 601 / cobas e 602 modules
    30 μL cobas e 801 module

  • Onboard stability

    28 days cobas e 411 analyzer, cobas e 601 / cobas e 602 modules
    16 weeks cobas e 801 module

  • Intermediate precision in positive samples

    cobas e 411 analyzer: CV 1.1 – 5.7 %
    cobas e 601 / cobas e 602 modules CV 4.0 – 6.0 %
    cobas e 801 module CV 3.4 – 4.3 %

  • Clinical sensitivity

    99.9 % (n = 1,025 confirmed HBsAg positive samples); 1 sample negative in all HBsAg assays tested

  • Analytical sensitivity

    PEI standard, subtype AD, 1985: ≤0.04 U/mL
    PEI standard, subtype AY, 1985: ≤0.04 U/mL
    WHO standard 00/588, subtype ad: ≤0.1 IU/mL

  • Mutant recognition

    112/115 tested mutants (native and recombinant) were correctly recognized; 3 samples negative in all HBsAg assays tested

  • Clinical specificity

    99.98 % (n = 6,360 blood donors)
    99.88 % (n = 3,593 hospitalized patients)



  1. WHO. Hepatitis B. Fact sheet N°204. Available at: http://www.who.int/mediacentre/factsheets/fs204/en, accessed November 2017. 
  2. Norder, H., Couroucé, A.M., Coursaget, P. et al. (2004 ). Genetic diversity of hepatitis B virus strains derived worldwide: genotypes, subgenotypes and HBsAg subtypes. Intervirology 47, 289-309. 
  3. Liaw,Y.F., Chu, C.M. (2009). Hepatitis B infection. Lancet 373, 582-592. 
  4. Gerlich, W. (2004). Diagnostic problems caused by HBsAg mutants – a consensus report of an expert meeting. Intervirology 47, 310-313. 
  5. Weber, B. (2005). Expert Rev Mol Diagn 5, 75-91.
  6. Gencay, M. et al. (2017). Ultra-deep sequencing reveals high prevalence and broad structural diversity of hepatitis B surface antigen mutations in a global population. PLoS One 12(5): e0172101.