Substantial variation in the hepatitis B surface antigen (HBsAg) in hepatitis B virus (HBV)-positive patients from South Africa: Reliable detection of HBV by the Elecsys HBsAg II assay

J Clin Virol. 2018 Apr;101:38-43. doi: 10.1016/j.jcv.2018.01.011. Epub 2018 Feb 6.


Background: It is essential that hepatitis B surface antigen (HBsAg) diagnostic assays reliably detect genetic diversity in the major hydrophilic region (MHR) of HBsAg to avoid false-negative results. Mutations in this domain display marked ethno-geographic variation and may lead to failure to diagnose hepatitis B virus (HBV) infection.

Objectives: Evaluate diagnostic performance of the Elecsys® HBsAg II Qualitative assay in a cohort of South African HBV-positive blood donors.

Study design: A total of 179 South African HBsAg- and HBV DNA > 100 IU/mL-positive blood donor samples were included. Samples were sequenced for genetic variation in HBsAg MHR using next-generation ultra-deep sequencing. HBsAg seropositivity was determined using the Roche Elecsys HBsAg II Qualitative assay. Mutation rates were compared between the first (amino acids 124-137) and second (amino acids 139-147) loops of the immunodominant MHR 'a' determinant region. Frequency of occult HBV infection-associated Y100C mutations was also determined.

Results: We observed a total of 279 MHR mutations (117 variants) in 102 (57%) samples, of which 91 were located in the 'a' determinant region. The major vaccine-induced escape mutation G145R was observed in two samples. All occult HBV infection-associated Y100C and common diagnostic and vaccine-escape-associated P120T, G145R, K122R, M133L, M133T, Q129H, G130N, and T126S mutations were reliably detected by the assay, which consistently detected the presence of HBsAg in all 179 samples including samples with 11 novel mutations.

Conclusions: Despite substantial variation in HBsAg MHR, the Elecsys HBsAg II Qualitative assay robustly detects HBV infection in this South African cohort.

Keywords: 454 sequencing; Chronic hepatitis B; HBsAg mutations; Immunoassay; Major hydrophilic region; Ultra-deep sequencing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Donors
  • DNA, Viral / genetics
  • Female
  • Genetic Variation
  • Genotype
  • Hepatitis B / diagnosis*
  • Hepatitis B Surface Antigens / chemistry
  • Hepatitis B Surface Antigens / genetics*
  • Hepatitis B Surface Antigens / immunology*
  • Hepatitis B Vaccines
  • Hepatitis B virus / genetics
  • Hepatitis B virus / immunology*
  • Hepatitis B virus / isolation & purification*
  • Hepatitis B, Chronic / diagnosis
  • Humans
  • Immunoassay / methods*
  • Immunodominant Epitopes / genetics
  • Immunodominant Epitopes / immunology
  • Male
  • Middle Aged
  • Mutation
  • Sensitivity and Specificity
  • South Africa
  • Young Adult


  • DNA, Viral
  • Hepatitis B Surface Antigens
  • Hepatitis B Vaccines
  • Immunodominant Epitopes