SOURCE: Ceccato A, Torres A, Cilloniz C, et al. Chest 2017;151:1311-1319.

In approximately half of the cases of community-acquired pneumonia (CAP), an etiologic agent is not identified. CAP caused by Streptococcus pneumoniae (pneumococcal pneumonia) often is categorized as “invasive” (the bacteria was cultured from body fluids such as blood or pleural fluid) vs. “noninvasive” (body fluid cultures were negative, but urine antigen testing for S. pneumoniae was positive). Curiously, only pneumonia confirmed by invasive methodology has been incorporated into epidemiologic reporting of CAP traditionally. Cecatto et al noted that clinicians probably are significantly underestimating the burden of CAP by limiting the “gold standard” definition to cases identified “invasively.”

The authors studied all cases of CAP (n = 5,132) in non-immunocompromised adults treated at their Barcelona, Spain, emergency department over a 14-year interval. Of these, only 15% were confirmed to be pneumococcal. Slightly more patients were confirmed to be infected by S. pneumoniae through urinary antigen testing (54%) than by body fluid cultures (46%). Additionally, the 30-day mortality was the same regardless of which tool confirmed the diagnosis, dispelling the notion that CAP diagnosed though the “invasive” path is more lethal. Both methods of diagnosis are valid indicators of the pathogen, but there is no reason to consider urine antigen testing as indicative of less pneumonia lethality.