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Hepatitis B Surface Antigen, Quantitative, Monitoring

Test code: 94333

Quantitation of HBsAg may help differentiate phases of HBV infection, evaluate prognosis, monitor response to treatment with immunomodulatory agents (e.g. pegylated interferon) or antiviral agents (i.e nucleoside and nucleotide analogs [NAs]), and guide decisions on treatment duration.1-4

Qualitative HBsAg testing is recommended to screen patients at risk for HBV infection and is one of the tests recommended as part of initial diagnosis. In contrast, quantitative HBsAg testing is not recommended for initial diagnosis but is useful for disease and treatment monitoring and management of patients with chronic hepatitis B infection  (see Question 1).1-4  

Quest Diagnostics uses an immunoassay method for quantitative HBsAg testing. The method employs the Ortho Vitros® system to construct a standard curve to calculate a quantitative HBsAg result. The WHO 3rd International standard reference serum (HBV genotype B4, HBsAg subtypes ayw1/adw2) was used to validate the values established for the calibration standard. Results are reported in IU/mL. 

The two assays have similar lower limits of detection: 0.085 IU/mL for qualitative HBsAg and 0.05 IU/mL for quantitative HBsAg. 

HBsAg is the main component of the outer virus envelope and is produced in excess during viral replication. Serum HBsAg level reflects the transcriptional activity of intrahepatic HBV covalently closed circular DNA (cccDNA), an indicator of viral protein synthesis.

No, quantitative HBsAg cannot replace HBV DNA measurement. However, it can provide additional value in conjunction with HBV DNA measurement to monitor chronic phases of HBV infection, define prognosis, and response to therapy. 1,4,6

The quantitative HBsAg level that best predicts sustained virologic response (or “cure”) has yet to be well established. A level of HBsAg less than 100 IU/mL in patients who are on nucleoside and nucleotide analogs (NA) treatment is associated with lower likelihood of relapse and therefore subsequent treatment.3,11-14

Published data show some concordance between these 2 assays in individual patients.8,9,10 However, some patients may have high levels of HBsAg but decreasing, low, or undetectable HBV DNA. This discordance may be related to differences in disease phase: HBsAg levels can be high because of active transcription of cccDNA, while HBV DNA levels can decrease or become undetectable because of decreasing DNA replication. Therefore, measurement of both HBsAg and HBV DNA can provide a more accurate clinical profile for an individual patient and help monitor and predict treatment outcomes. The information gained with both results, even if discordant, can provide additional insights into the patient’s prognosis. 

The five phases of chronic HBV (CHB) infection are listed below. Alanine aminotransferase (ALT), hepatitis B e antigen (HBeAg), and HBV DNA levels can help determine the phase of infection, and monitoring can help inform patient management (Table below). 

Click the table to open in new tab (enlarged)

If there is overlap in ALT and HBV DNA patterns between phases, these markers alone are not sufficient to identify the exact phase of disease.1 Analysis of multiple markers of HBV infection will help determine disease phase and potential treatment options. HBeAg status and HBsAg are additional markers that can be useful for prognosis and therapeutic decision-making in patients with different phases of infection.1,3,4

References

  1. World Health Organization. Guidelines for the prevention, diagnosis, care and treatment for people with chronic hepatitis B infection. Published 29 March 2024. Website: https://iris.who.int/bitstream/handle/10665/376353/9789240090903-eng.pdf?sequence=1. Accessed April 18, 2025.
  2. Terrault NA, Lok ASF, McMahon BJ, et al. Update on prevention, diagnosis, and treatment of chronic hepatitis B: AASLD 2018 hepatitis B guidance. Clin Liver Dis (Hoboken). 2018 Aug 22;12(1):33-34. doi:10.1002/cld.728
  3. Ghany MG, Pan CQ, Lok AS, et al. AASLD/IDSA Practice Guideline on Treatment of Chronic Hepatitis B. Hepatology. 2025 Nov 4. doi:10.1097/HEP.0000000000001549
  4. Cornberg M, Sandmann JJ, Kennedy P, et al. EASL Clinical Practice Guidelines on the management of hepatitis B virus infection. J Hepatol. 2025 Aug;83(2):502-583. doi:10.1016/j.jhep.2025.03.018
  5. Sarin S, Kumar M, Lau G, et al. Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update. Hepatol Int. 2016;10:1-98. doi:10.1007/s12072-015-9675-4
  6. Höner Zu Siederdissen C, Cornberg M. The role of HBsAg levels in the current management of chronic HBV infection. Ann Gastroenterol. 2014;27:105-112.
  7. Wong G, Chan H. Use of quantitative hepatitis B surface antigen with hepatitis B virus DNA in clinical practice. Clin Liver Dis. 2013;2:8-10. doi:10.1002/cld.165
  8. Tatar B, Acar A, Pelin A, et al. Role of quantitative hepatitis B surface antigen levels in predicting liver biopsy time in treatment-naive chronic hepatitis B patients. Clin Exp Hepatol. 2020 Feb 17;6(1):55-59. doi:10.5114/ceh.2020.9305
  9. Yang N, Feng J, Zhou T, et al. Relationship between serum quantitative HBsAg and HBV DNA levels in chronic hepatitis B patients. J Med Virol. 2018 Jul;90(7):1240-1245. doi:10.1002/jmv.25080
  10. Karra VK, Chowdhury SJ, Ruttala R, et al. Clinical Significance of Quantitative HBsAg Titres and its Correlation With HBV DNA Levels in the Natural History of Hepatitis B Virus Infection. J Clin Exp Hepatol. 2016 Aug 3;6(3):209-215. doi:10.1016/j.jceh.2016.07.002
  11. Tseng T, Liu C, Su T, et al. Serum hepatitis B surface antigen levels predict surface antigen loss in hepatitis B e antigen seroconverters. Gastroenterology. 2011;141:517–525.
  12. Kranidiotia H, Manolakopoulosb S, Khakooa SI. Outcome after discontinuation of nucleot(s)ide analogues in chronic hepatitis B: relapse rate and associated factors. Ann Gastroenterol. 2015;28:173-181.
  13. Lee JM, Ahn SH, Kim HS, et al. Quantitative hepatitis B surface antigen and hepatitis B e antigen titers in prediction of treatment response to entecavir. Hepatology. 2011;53:1486-1493.
  14. Sonneveld MJ, Rijckborst V, Boucher C, et al. Prediction of sustained response to peginterferon alfa-2b for hepatitis B e antigen–positive chronic hepatitis B using on-treatment hepatitis B surface antigen decline. Hepatology. 2010; 52: 1251–1257.

 

This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

Document FAQS.192 Version: 1

Version 1: effective 04/16/2026 to present

Version 0: Effective 08/01/2017 to 04/16/2026

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