Invasive Disease vs Urinary Antigen-Confirmed Pneumococcal Community-Acquired Pneumonia

BACKGROUND: The burden of pneumococcal disease is measured only through patients with invasive pneumococcal disease. The urinary antigen test (UAT) for pneumococcus has exhibited high sensitivity and specificity. We aimed to compare the pneumococcal pneumonias diagnosed as invasive disease with pneumococcal pneumonias defined by UAT results. METHODS: A prospective observational study of consecutive nonimmunosuppressed patients with community-acquired pneumonia was performed from January 2000 to December 2014. Patients were stratified into two groups: invasive pneumococcal pneumonia (IPP) defined as a positive blood culture or pleural fluid culture result and noninvasive pneumococcal pneumonia (NIPP) defined as a positive UAT result with negative blood or pleural fluid culture result. RESULTS: We analyzed 779 patients (15%) of 5,132, where 361 (46%) had IPP and 418 (54%) had NIPP. Compared with the patients with IPP, those with NIPP presented more frequent chronic pulmonary disease and received previous antibiotics more frequently. Patients with IPP presented more severe community-acquired pneumonia, higher levels of inflammatory markers, and worse oxygenation at admission; more pulmonary complications; greater extrapulmonary complications; longer time to clinical stability; and longer length of hospital stay compared with the NIPP group. Age, chronic liver disease, mechanical ventilation, and acute renal failure were independent risk factors for 30-day crude mortality. Neither IPP nor NIPP was an independent risk factor for 30-day mortality. CONCLUSIONS: A high percentage of confirmed pneumococcal pneumonia is diagnosed by UAT. Despite differences in clinical characteristics and outcomes, IPP is not an independent risk factor for 30-day mortality compared with NIPP, reinforcing the importance of NIPP for pneumococcal pneumonia.