The Hepatitis B Surface Antigen (HBsAg) Quantitative test measures the level of HBsAg in the blood, helping to assess and monitor Hepatitis B virus (HBV) infection. Unlike a qualitative test, which only detects the presence of the antigen, this test provides a numerical value, offering insights into disease progression and response to treatment.

Importance

HBsAg is the first detectable marker of HBV infection, appearing before symptoms develop. A quantitative measurement helps differentiate between acute and chronic infection, predict treatment response, and monitor viral activity over time. This test is critical for individuals undergoing antiviral therapy, as decreasing levels indicate effective treatment.

When Is It Done?

To diagnose active HBV infection

To differentiate between acute and chronic HBV infection

To monitor disease progression in chronic Hepatitis B patients

To evaluate response to antiviral therapy

To assess HBV carrier status in high-risk individuals

To screen for HBV before organ transplantation or immunosuppressive therapy