HOW TO TEST FOR CHRONIC HBV INFECTION AND MONITOR TREATMENT RESPONSE. In settings or populations with an HBsAg seroprevalence of ≥0.4%, a single serological assay for detection of HBsAg is recommended, prior to further evaluation for HBV DNA and staging of liver disease. In settings or populations with a low HBsAg seroprevalence of <0.4%, confirmation of HBsAg positivity on the same immunoassay with a neutralization step or a second different rapid diagnostic test (RDT) assay for detection of HBsAg may be considered.