title: Do we need an 'in-house' neutralization assay for confirmation of hepatitis B surface antigen? Answers from a tertiary care hospital in India.
abstract: OBJECTIVE
  Hepatitis B surface antigen (HBsAg) is an important serological marker for diagnosis of hepatitis B virus (HBV) infection. Commercial kits for detection of HBsAg emphasize confirmation by neutralization assays. In this study, we have standardized an 'in-house' neutralization test for HBsAg confirmation.
  
  
  METHODS
  Among 6684 HBsAg-positive samples, 615 were subjected to an 'in-house' HBsAg neutralization test (NT). Of these, 91 (100%) high-reactive samples (optical density [OD] 1.000-3.000) and 286 (93%) of 289 low-reactive samples (OD < 1.000) were neutralized, and 235 (100%) grey-zone reactive samples were 'in-house' NT negative. Eighty-four samples of varying reactivities that were tested by the 'in-house' NT were compared with a commercial NT (AxSYM, Abbott).
  
  
  RESULTS
  The 'in-house' NT showed an excellent agreement (kappa = 0.83, P < 0.001) with the commercial confirmatory assay. The sensitivity, specificity, positive and negative predictive values were 90%, 94%, 96% and 87%, respectively.
  
  
  CONCLUSIONS
  The enzyme immunoassay-based 'in-house' HBsAg neutralization assay is a feasible alternative to the commercial HBsAg confirmatory assay. This technique is easily adaptable, cost-effective and reliable for the confirmation of HBsAg in a low resource setting, enhancing the overall quality of HBsAg screening.
authors.affiliation: Department of Clinical Virology, Christian Medical College, Vellore, India.
authors.forename: Gnanadurai J
authors.initials: GJ
authors.lastname: Fletcher
authors.forename: Manu
authors.initials: M
authors.lastname: Gnanamony
authors.forename: Joel
authors.initials: J
authors.lastname: David
authors.forename: Ashrafali M
authors.initials: AM
authors.lastname: Ismail
authors.forename: Thenmozhi
authors.initials: T
authors.lastname: Subramani
authors.forename: Priya
authors.initials: P
authors.lastname: Abraham
mesh_terms: D015415:Biomarkers / Q000097:blood; D005240:Feasibility Studies; D006509:Hepatitis B / Q000175:diagnosis*; D006514:Hepatitis B Surface Antigens / Q000097:blood*; D006515:Hepatitis B virus / Q000276:immunology*; D006784:Hospitals, Teaching / Q000592:standards; D006801:Humans; D007124:Immunoenzyme Techniques / Q000592:standards; D007194:India; D009500:Neutralization Tests / Q000592:standards; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D006514:Hepatitis B Surface Antigens; D011933:Reagent Kits, Diagnostic