Routine ordering of Streptococcus pneumoniae urine antigen is discouraged for community-acquired pneumonia, especially in non-severe cases

Streptococcus pneumoniae antigen tests (SPUAT) are intended to rapidly detect pneumococcal antigens from urine of adult patients to aid in the diagnosis of community acquired pneumonia (CAP), but due to the lower sensitivity the test (approximately 60-65%), a negative test cannot rule out S. pneumoniae as the etiologic agent of CAP.^1,2 Current therapeutic regimens include antibiotics with activity against S. pneumoniae, therefore even if a test is positive it does not alter empiric therapy in most cases. Because other pathogens, in addition to S. pneumoniae, may be contributing to CAP, antimicrobial therapy is not often de-escalated and there is concern for clinical relapse.³

2024 IDSA/ASM guidelines for diagnostic testing and 2019 ATS/IDSA guidelines on treatment of CAP state that if antigen test is available it should only be considered for severe CAP in hospitalized patients.^3,4 Although studies have found higher positivity rates for SPUATs in severe pneumonia and in patients admitted to the intensive care unit, the recommended empiric regimens for that patient population are effective against S. pneumoniae. In addition, providers are less likely to deescalate antibiotics in this high-risk population, therefore the value of the antigen test is questionable. ^1,3 Given the prevalence of CAP as a presenting diagnosis and that clinical characteristics of patients do not strongly correlate with a positive SPUAT,^1,2 widespread utilization of a diagnostic test is an inefficient use of laboratory resources when the test has limited potential to impact clinical care and antibiotic utilization.