HBsAg is the earliest marker of Hepatitis B Virus (HBV) infection.

The card test is a rapid diagnostic method that gives results within 15–20 minutes.

Clinical uses include:

Screening for Hepatitis B infection in clinics, blood banks, and camps.

Identifying individuals who require confirmatory testing (ELISA, CLIA, or PCR).

Supporting public health programs for HBV control.

While convenient, the card test is less sensitive and specific compared to ELISA or CLIA.

Positive results must be confirmed with HBV DNA PCR or other advanced assays.

Analyte: Hepatitis B surface antigen (HBsAg) in serum/plasma/whole blood.

Normal Result: Negative (no HBsAg detected).

Abnormal Findings:

Positive card test: Indicates acute or chronic Hepatitis B infection; requires confirmatory testing.

Persistent positivity (>6 months): Suggests chronic HBV carrier state.

Clinical Use:

Provides a rapid, point‑of‑care screening tool for HBV infection.

Helps prevent HBV transmission via blood transfusion.

Supports early detection and referral for confirmatory testing and treatment.