This is a cross sectional observational study to asses the performance of two novel HBV DNA testing methodologies; a) dried blood spot sampling and b) fingerstick capillary blood using the Xpert® Hepatitis B Virus viral load assay. Both novel testing methodologies will be compared with venous blood tested using a gold standard HBV DNA assay. The sensitivity and specificity of the two novel testing will be evaluated.

HBV viral load tests are essential to guide antiviral treatment eligibility and effectiveness. However, many people are unable to access these tests, particularly those living in remote or limited resources settings given high cost, or unavailable infrastructure. Simple, affordable and accessible HBV viral load tests are required to increase global access to HBV testing and treatment to meet the WHO HBV elimination targets. The GeneXpert Diagnostic Systems, the most common molecular point-of-care platform globally, has the potential to provide simple and affordable HBV viral load tests. Dried Blood Spot testing is also an affordable and accessible testing methodology particularly suited to remote and resource limited settings. This proof-of-concept study will assess the feasibility and diagnostic performance of Xpert® HBV Viral Load test and Dried Blood Spot testing for the quantitation of HBV DNA from fingerstick capillary samples.

This study will be a cross-sectional observational study and will assess the performance of a novel fingerstick HBV Viral Load and Dried Blood Spot tests within a total of 300 participants who will be recruited across a network of hepatitis clinics in Sydney, Australia. No treatment will be administered as part of this study.

The Xpert HBV cartridge will be adapted to use fingerstick capillary blood instead of processed whole blood, and it's performance measured against a gold standard venous blood HBV DNA assay. Dried Blood Spot HBV DNA testing performance will also be measured against the gold standard venous blood HBV DNA assay.

Secondary objectives of the study are to: 1) evaluate diagnostic performance of the Xpert® HBV Viral Load assay compared to standard of care testing, by patients' hepatitis B e-antigen status (among e-antigen positive and e-antigen negative patients). 2) Evaluate diagnostic performance of the Xpert® HBV Viral Load assay compared to standard of care testing, by HBV treatment status (among treatment naïve patients and those receiving treatment). 3) Evaluate diagnostic performance of the Xpert® HBV Viral Load assay compared to standard of care testing, by HBV DNA levels (among patients with HBV DNA <20 IU/mL; between 20 and 2,000 IU/mL, between 2,000 and 20,000 IU/mL; between 20,000 and 200,000 IU/mL; and >200,000 IU/mL).

Inclusion Criteria:

• Have voluntarily signed the informed consent form, 18 years of age or older, HBsAg positive

Exclusion Criteria:

• Nil

Participants will be recruited from across the network of tertiary hepatitis clinics active in providing HBV clinical care. All participants must meet the inclusion criteria to be eligible to participate in the study.

Participants will be recruited irrespective of HBV DNA Level, HBeAg or treatment status.