Rethinking Pneumococcal Urinary Antigen Testing in the Emergency Department: From Reflex Testing to Reasoned Use

Pneumococcal urinary antigen testing (PUAT) is often ordered reflexively in the emergency department (ED) because it is rapid and noninvasive. However, the ED-relevant question is not whether PUAT can detect pneumococcal antigen, but whether it reliably changes what clinicians do next: initial antibiotic selection and/or early narrowing, diagnostic strategy, disposition, and ultimately patient outcomes. The accuracy of PUAT depends on the population being tested; in cohorts enriched for confirmed pneumococcal pneumonia, performance can be overestimated. In the ED, a negative PUAT cannot reliably rule out pneumococcal disease. In addition, PUAT cannot identify polymicrobial infection, and positive results can be misinterpreted without attention to clinical context (e.g., recent infection, polysaccharide vaccination, and carriage biology). Consequently, routine PUAT may become a low-yield ritual with limited decision impact. We propose redesigning PUAT around actionability: order PUAT only when a positive result would plausibly support narrowing antibiotics in a clinically appropriate context (low aspiration and limited concern for polymicrobial infection) and when reliable sputum information is unavailable. A simple "3C" framework can help shift PUAT from reflex testing to reasoned use in ED practice.