Utility and clinical impact on the reported aetiology of a urinary antigen-detection test for Streptococcus pneumoniae in community-acquired pneumonia at the emergency department

Abstract number: 1733_648

Ezpeleta G., Ezpeleta C., Alava J.A., Unzaga J., Cabezas V., Gerediaga I., Amezua B., Blanco R., Cisterna R.

Objectives: The diagnosis of severe pneumococcal infections is inadequate, relying heavily on culture of Streptococcus pneumoniae from blood or other normally sterile fluids, and is severely limited by prior administration of antibiotics. We evaluated prospectively the Binax NOW S. pneumoniae urinary antigen test, a rapid immunochromatographic (ICT) assay, for the diagnosis of bacteraemic pneumococcal infections in adult patients with community lower respiratory tract infection (CLRTI) at the emergency room.

Methods: One thousand, two hundred and thirty three adult patients with CLRTI who were admitted to the hospital were studied prospectively between January 2004 and September 2006. The ICT test was performed on fresh unconcentrated urine following the manufacturer instructions. The results of the ICT test were compared with blood culture ones, and sensibility, specificity and likehood positive and negative ratios were calculated.

Results: The ICT assay was positive in 298 (24.15%) of 1,233 patients enrolled into the study and in 78 (79.59%) of 98 patients with pneumococcal pneumonia confirmed by conventional methods. The test revealed a sensitivity of 75.9% (71.2–83.1) and a specificity of 94.0% using conventional microbiological criteria as the gold standard. The likehood positive ratio value was 12.65, and the negative one was 3.9. The diagnostic yield of pneumococcal pneumonia was increased using ICT combined with conventional methods. Antigen was still detectable in 53% of patients during treatment

Conclusion: The ICT to detect S. pneumoniae urinary antigen is therefore a rapid and useful method for diagnosing pneumococcal pneumonia. Detection of urinary antigen is a valuable, sensitive, and rapid test for the early diagnosis of bacteraemic pneumococcal infections in adult patients, even after antibiotic treatment has commenced