Streptococcus pneumoniae is one of the most common causes of community-acquired pneumonia. Pneumococcal pneumonia can progress to meningitis and septicemia.Traditionally, physicians started patients on empirical antibiotic therapy until bacterial culture results were reported. The availability of a rapid test facilities the prescription of the most appropriate antibiotic much sooner.
A pneumococcal antigen test (Binax NOW) is an immunochromatographic membrane assay that detects the cell wall C-polysaccharide that is common to all serotypes of S. pneumoniae. The test can be performed on urine or cerebrospinal fluid. Results are available approximately 15 minutes after adding specimen to the test device.
A Cochrane study determined the sensitivity was 99.5% and specificity 98.2% in CSF.
This test can remain positive in up to 90% of infected patients after one week of antimicrobial therapy. The test may also be positive in patients who have received the Streptococcus pneumoniae vaccine within 5 or fewer days prior to testing.
Test results are reported as negative or positive.
The specimen requirement is 10 mL urine from a random collection or 1 mL of CSF. Reference value is a negative result.
References
Someko H, et al, Diagnostic accuracy of rapid antigen tests in cerebrospinal fluid for pneumococcal meningitis: a systematic review and meta-analysis, Clinical Microbiol Infect, 2023;29(3):310-319.
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