Streptococcus pneumoniae Antigen, Qualitative

What This Test Looks For

Streptococcus pneumoniae (often called pneumococcus) is a common bacterium that can infect the lungs, the membranes around the brain and spinal cord, the bloodstream, and the ears and sinuses. This test looks for specific antigen proteins from the bacteria in a sample such as urine, cerebrospinal fluid, or other body fluid. Detecting these antigens gives your care team evidence that pneumococcus is likely involved in your infection.

Why Your Doctor Ordered It

Your doctor may order this test when you have signs of a serious infection—such as fever, cough, stiff neck, headache, or confusion—and they need to identify the cause quickly. Because pneumococcus is a leading cause of bacterial pneumonia and meningitis, confirming or ruling it out helps guide the choice and timing of antibiotics. The test can be especially useful when standard culture results take time to return.

How the Sample Is Collected

Depending on your symptoms, the sample may be urine or a body fluid such as cerebrospinal fluid collected during a spinal tap. Urine collection is simple and non-invasive; you provide a sample in a sterile cup. Cerebrospinal fluid is collected by a clinician using a small needle in the lower back. Your care team will explain the specific collection method appropriate for your situation.

Understanding Your Results

A positive result means pneumococcal antigens were detected, suggesting these bacteria are likely part of the infection. A negative result means they were not detected, which makes pneumococcal infection less likely but does not completely rule it out. Results are interpreted together with your symptoms, other lab tests, and imaging. Your doctor will explain what your result means for your care; no single number or reference range applies to every patient.