Serum or plasma concentration of pneumococcal polysaccharide antigen (via immunoassay)

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like high fever, chills, confusion, or difficulty breathing—especially if you’ve been exposed to pneumococcal bacteria or have a weakened immune system. It’s also used in certain high-risk groups, such as those with chronic lung disease, asplenia, or recent travel to areas with high infection rates.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, typically drawn from a vein in your arm. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Positive results indicate the presence of pneumococcal antigens, which may confirm a pneumococcal infection. Negative results mean no detectable antigens were found in this sample, but further testing or observation may be needed.

Common Causes of Positive Results

A positive result is most likely due to active pneumococcal infection (e.g., pneumonia, meningitis, or bloodstream infection). Rarely, it could appear in people with recent vaccination or prior exposure without active disease.