Background: A serotype-specific urinary antigen detection assay (UAD) for 13 serotypes included in the pneumococcal conjugate vaccine (PCV13) was recently reported as a useful diagnostic tool for pneumococcal pneumonia. We aimed to assess the diagnostic accuracy of the UAD in HIV-infected South African adults.
Methods: Urine specimens from a well-defined cohort of HIV-infected South African adults with pneumonia were evaluated retrospectively in the UAD assay. Pneumonia was considered pneumococcal if either sputum Gram stain, sputum culture, blood culture or immunochromatographic (ICT) BinaxNow® S. pneumoniae test (composite diagnostic) were positive.
Results: Among 235 enrolled pneumonia patients, the UAD was more frequently positive (104 [44.3%]) than the composite diagnostic (71 [30.2%], p<0.001) and increased the pneumococcal etiology from 30.2% by an additional 22.6% to 52.8%. The UAD assay detected more pneumococcal etiologies (45.0%) than the serotype-independent ICT (23.4%, p<0.001). The UAD identified 6/7 patients with PCV13 serotype bacteremia without misclassification of bacteremia episodes due to non-PCV13 serotypes. The UAD was positive in 5.1% of asymptomatic HIV-infected persons with higher rates among those with nasopharyngeal carriage. Concordance between serotypes identified by UAD and by Quellung and PCR serotyping was 70/86 (81.4%). The UAD identified the dominant serotype in multiple serotype carriage.
Conclusions: This study confirms the utility of the UAD assay in HIV-infected adults comparing favourably with other diagnostic tests. A high-valent UAD may become a new standard for detection of pneumococcal pneumonia in adults. Prior to PCV introduction, at least 53% of pneumonias were due to pneumococcus in HIV-infected South African adults.