Evaluation of Urinary Antigen Test for Rapid Diagnosis of Community-Acquired Pneumococcal Pneumonia

Ryoo, Nam Hee; Ha, Jung Sook; Jeon, Dong Suk; Kim, Jae Ryong

Abstract

BACKGROUND: Streptococcus pneumoniae is one of the most common pathogens of communityacquired pneumonia (CAP) which needs rapid diagnosis and appropriate therapeutic approaches. We evaluated a new rapid urinary antigen test kit, NOW S. pneumoniae antigen test (Binax Inc., Maine, USA), for the detection of the S. pneumoniae antigen in the urine of patients who were suspected of CAP.
METHODS
A total of 115 urine samples were tested during April to July, 2004. Patients were divided into 2 groups: the first was the patients who were suspected of CAP and the second was the patients with other disorders. Urinary antigen test was performed done by immunochromatographic methods and results were read within 15 minutes. All the urine samples were random and unconcentrated. The patients were reviewed clinically, together with the results of sputum and blood cultures, urinalysis and other laboratory tests.
RESULTS
Overall mean age was 62-years old and male proportion was 59%: Group 1 had mean age of 63-years old and male 54% whereas group 2 had 60-years old and 76%. S. pneumoniae antigen was detected in the urine from 14 (12.2%) of 115 patients. Of the 14 patients with positive urinary antigen tests, 12 were from 90 patients with CAP with fever, leukocytosis and appropriate radiological findings, giving the sensitivity of 13.3%; the remaining 2 patients were from 25 patients with other disorders. Only 2 of the 12 patients showed S. pneumoniae in sputum or blood cultures, respectively. Urinary antigen was not detected in 23 of the 25 patients with other disorders, giving the specificity of 92%.
CONCLUSIONS
Since this simple and rapid urinary antigen test showed low sensitivity in this study, the clinical symptoms and signs and radiological findings of patients should be reviewed together with the results of the urine test for early and accurate diagnosis and treatment, consistent clinical symptoms and signs with radiological studies are inevitable. Thus further studies would be necessary. The urinary antigen test showed high specificity and therefore should be a useful adjunct to cultures to be in aid of the diagnosis of CAP.