Urinary antigen testing for pneumococcal pneumonia: is there evidence to make its use uncommon in clinical practice?

Microbiological confirmation of Streptococcus pneumoniae pneumonia remains challenging, as culture from blood or pleural fluid is positive in only 15-30% cases. It was hoped that a commercially available urine antigen test would improve diagnosis and consequently patient care, with improved antimicrobial stewardship. Urine antigen testing for pneumococcal pneumonia is recommended in current BTS guidelines, whilst NICE and ATS/IDSA guidelines consider its usage. Urine antigen testing is therefore widely used in hospital medicine. The assay is non-invasive, simple and culture independent, producing a result within 15 minutes. Whilst initial evidence suggested urine antigen testing had a high sensitivity, recently data has suggested the actual sensitivity is lower than expected, at approximately 60-65%. Evidence has also emerged indicating that clinicians infrequently rationalise antibiotics following positive urine antigen testing, with multiple publications evaluating the role of urine antigen testing in clinical care. Furthermore, urine antigen testing does not appear to lead to any cost saving or reduction in length of hospital stay. We therefore conclude that the pneumococcal urinary antigen test does not alter patient management and leads to no cost saving, and has a lower than expected accuracy. Therefore it may be time make its use uncommon in clinical practice.