Pneumococcal urinary antigen test: diagnostic yield and impact on antibiotic treatment

The pneumococcal urinary antigen test (PUAT) is commonly used for the etiological diagnosis of community-acquired pneumonia (CAP) and can be useful for targeting pathogen-directed therapy.

The aim of our study was to evaluate the diagnostic yield of the PUAT and the impact of a positive PUAT result on antibiotic treatment in patients with CAP in a clinical non-research setting.

Adults hospitalized with CAP between January 2005 and November 2007 were studied retrospectively. All patients were tested by PUAT. The sensitivity of the PUAT was determined and changes in antibiotic therapy were assessed.

A total of 681 patients with CAP were included. The microorganism most frequently identified was Streptococcus pneumoniae. It was found in 95 (14.0%) patients, and the PUAT increased the diagnostic yield to a total of 184 (27.0%) patients. The S. pneumoniae antigen was detected in 37 of 55 patients with definitive pneumococcal pneumonia (67.3%). Pneumococcal urinary antigen was positive in 56 of 95 pneumococcal cases (definite and probable), resulting in an overall test sensitivity of 59.0%. Positive results of the PUAT led physicians to narrow the spectrum of antibiotic treatment in 69 (45.1%) patients.

The PUAT is a useful method for early detection of S. pneumoniae in patients with CAP, but the test was less sensitive in this clinical setting than prospective studies indicated. The PUAT results led physicians to narrow the spectrum of antibiotic treatment in approximately half of the relevant cases, which limited the impact of a positive PUAT.