Current and potential usefulness of pneumococcal urinary antigen detection in hospitalized patients with community-acquired pneumonia to guide antimicrobial therapy.

BACKGROUND: The role of pneumococcal urinary antigen detection in the treatment of adults with community-acquired pneumonia (CAP) is not well defined. We assessed the usefulness of pneumococcal urinary antigen detection in the diagnosis and antimicrobial guidance in patients hospitalized with CAP.
METHODS: A prospective study of all adults hospitalized with CAP was performed from February 2007 through January 2008. To evaluate the accuracy of the test, we calculated its sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios. The gold standard used for diagnosis of pneumococcal pneumonia was isolation in blood or pleural fluid (definite diagnosis) and isolation in sputum (probable diagnosis). Antibiotic modifications, complications, and mortality were analyzed.
RESULTS: A total of 474 episodes of CAP were included. Streptococcus pneumoniae was the causative pathogen in 171 cases (36.1%). It was detected exclusively by urinary antigen test in 75 cases (43.8%). Sixty-nine patients had CAP caused by a pathogen other than S pneumoniae. Specificity was 96%, positive predictive value ranged from 88.8% to 96.5%, and the positive likelihood ratio ranged from 14.6 to 19.9. The results of the test led the clinicians to reduce the spectrum of antibiotics in 41 patients. Pneumonia was cured in all of them. Potentially, this optimization would be possible in the 75 patients diagnosed exclusively by the test.
CONCLUSION: When its findings are positive, the pneumococcal urinary antigen test is a useful tool in the treatment of hospitalized adult patients with CAP because it may allow the clinician to optimize antimicrobial therapy with good clinical outcomes.