Incidence and impact of false-positive urine pneumococcal antigen testing in hospitalized patients

Immunochromatographic urine pneumococcal antigen testing (ICT) has become a common diagnostic tool for those presenting with possible invasive pneumococcal disease. The incidence and clinical impact of ICT false-positivity on hospitalized patients has not been assessed outside of specific patient subpopulations. ICT performance needs to be assessed in a real-world clinical setting. This study aims to describe the incidence and clinical impact of ICT false-positivity in a hospital setting over a 19-month period.

A retrospective cohort study was performed to assess the incidence of false-positive (FP) ICT among hospitalized patients from November 21, 2007 to June 30, 2009. The primary objective was to describe the incidence of FP ICT results. The secondary objective was to describe what clinical impact, if any, could be attributed to FP ICT results.

During the study period, 52 positive ICT results were obtained, of which 5 (9.6%) were deemed falsely positive. Interestingly, two of the 5 FP results were from patients who had received 23-valent pneumococcal vaccine (PPV) in the 2 days prior to ICT. The management of all 5 patients was impacted by the FP results through unnecessary antimicrobial treatment and/or deferral of further clinical evaluation.

Health care providers should be aware of the potential for ICT FP and should order and interpret these tests within an informed clinical framework.