Serum or Plasma Substance Concentration for Pneumococcal Polysaccharide Antigen (Qualitative)

What This Test Measures

The test looks for specific antigens produced by *Streptococcus pneumoniae*, a common cause of pneumonia, meningitis, and other serious infections. These antigens are fragments of the bacteria’s outer coat that the immune system recognizes. If present in your blood, they suggest recent bacterial infection.

Why It’s Done

Your healthcare provider may order this test if you have symptoms like high fever, chest pain, confusion, or severe headache—especially if you’re at higher risk for pneumococcal infections (e.g., elderly adults, people with weakened immune systems, or those with chronic health conditions).

Sample Collection and Preparation

A blood sample is drawn from a vein, typically in your arm. The blood is processed to separate serum or plasma (the liquid part without clotting factors) for testing. This test does not require fasting.

Test Limitations

This is a qualitative test, meaning it only tells you *if* the antigen is present, not how much. Results may not be available immediately, and false positives or negatives can occur, especially in early or late stages of infection.