title: Elecsys hepatitis B surface antigen quantitative assay: performance evaluation and correlation with hepatitis B virus DNA during 96 weeks of follow-up in chronic hepatitis B patients.
abstract: BACKGROUND
  Treatment for chronic hepatitis B aims to suppress virus replication and virus sequestration in hepatocytes. Covalently closed circular (ccc) DNA is the template for transcription of viral genes and is responsible for viral persistence. However, limited data are available for quantification of hepatitis B surface antigen (HBsAg) in Korea.
  
  
  METHODS
  We evaluated the Elecsys HBsAg II quant assay (Roche Diagnostics, USA) for within-run, between-run, and between-day precisions, linearity, carryover, and clinical specificity. In total, 156 serum samples were evaluated for correlation between HBsAg and hepatitis B virus (HBV) DNA. Serial samples were obtained from 10 patients at 0, 12, 24, 48, 72, and 96 weeks during follow-up.
  
  
  RESULTS
  The assay detected HBsAg in a linear range of 0.5-48,696 IU/mL. Within-run, between-run, and between-day CVs were 2.9-4.1%, 0-1.5%, and 1.5-4.9%, respectively. Cross-reactivity between potentially interfering substances was absent, and the carryover rate was 0.00002%. The correlation of measurements between the Elecsys assay and HBV DNA PCR was weak (r=0.438, P=0.002). For predicting virologic response, cutoff values of 10,275 IU/mL and 3,846 IU/mL at 12 and 24 weeks after treatment initiation showed positive predictive values of 77.1% and 85% and negative predictive values of 84.6% and 50%, respectively.
  
  
  CONCLUSIONS
  The Elecsys HBsAg II quant assay showed good performance for precision, linearity, carryover rate, and specificity. HBsAg level at baseline, 12 weeks, and 24 weeks after treatment initiation can predict virologic response, and the assay can be used for HBsAg quantification in clinical practice.
authors.affiliation: Department of Laboratory Medicine, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Hyun Ji
authors.initials: HJ
authors.lastname: Lee
authors.forename: Shine Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Sun Min
authors.initials: SM
authors.lastname: Lee
authors.forename: Jeong
authors.initials: J
authors.lastname: Heo
authors.forename: Hyung Hoi
authors.initials: HH
authors.lastname: Kim
authors.forename: Chulhun L
authors.initials: CL
authors.lastname: Chang
authors.forename: Eun Yup
authors.initials: EY
authors.lastname: Lee
authors.forename: Han Chul
authors.initials: HC
authors.lastname: Son
mesh_terms: D000704:Analysis of Variance; D000998:Antiviral Agents / Q000627:therapeutic use; D004279:DNA, Viral / Q000032:analysis; D005500:Follow-Up Studies; D006514:Hepatitis B Surface Antigens / Q000097:blood*; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism*; D019694:Hepatitis B, Chronic / Q000188:drug therapy / Q000821:virology*; D006801:Humans; D016133:Polymerase Chain Reaction; D012372:ROC Curve; D011933:Reagent Kits, Diagnostic; D013997:Time Factors
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D011933:Reagent Kits, Diagnostic
keywords: Chronic hepatitis B; HBsAg; Hepatitis B virus; Quantification