Pneumococcus Urine Antigen
Streptococcus pneumoniae is one of the most common causes of community-acquired pneumonia. Conventional microbiologic tests have variable efficacy for detection of S. pneumoniae respiratory infections. The sensitivity of blood and sputum cultures can be as low as 30% and 60% respectively.
A Pneumococcal urine antigen test is available. This is a rapid immunochromatographic membrane assay that detects cell wall C-polysaccaride that is common to all serotypes of S. pneumoniae. The sensitivity of the S. pneumoniae urine antigen test is reportedly the highest in adults having pneumonia with bacteremia (87%). Sensitivity is slightly lower with bacteremia only (80-82%), and overall specificity is 95%. Additionally, this test can remain positive in up to 90% of infected patients after one week of antimicrobial therapy. Although urine antigen is moderately sensitive and highly specific in adults, it has limited utility in children, due to high rates of nasopharyngeal colonization with S. pneumoniae.
Specimen requirement is 10 mL urine from a random collection, and testing can be performed on the same specimen submitted for Legionella urine antigen testing.
