HIV p24 Antigen (Qualitative) – Serum

What This Test Measures

The HIV p24 antigen is a protein produced by the HIV virus shortly after infection. This test identifies its presence in your blood, which can signal an active infection—even before antibodies develop. It’s often used as an initial screening tool, especially in high-risk groups or when testing for acute HIV.

Why It’s Done

Your healthcare provider may order this test if you have symptoms of infection (e.g., fever, fatigue), recently had unprotected sex, shared needles, or were exposed to HIV. It may also be used in routine screening for people at higher risk, such as sexually active individuals without protection or those with multiple sexual partners.

How It Works

The test uses a qualitative immunoassay (likely a chemiluminescent or fluorescence-based method) to detect p24 antigen in your serum. If the test is positive, it means the virus is actively replicating, but it does not confirm HIV infection alone—additional antibody testing is required for diagnosis.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample via a simple venipuncture (needle draw). If you’re nervous, let your provider know—they can offer reassurance or distraction techniques.