The etiologic diagnosis of community-acquired pneumonia (CAP) remains challenging in children because blood cultures have low sensitivity. Novel approaches are needed to confirm the role of Streptococcus pneumoniae.
In this study, pneumococcal etiology was determined by serology using a subset of blood samples collected during a prospective multicentre observational study of children <15 years of age hospitalized in Belgium with radiogram-confirmed CAP. Blood samples were collected at admission and 3–4 weeks later. Pneumococcal (P)-CAP was defined in the presence of a positive blood or pleural fluid culture. Serotyping of S. pneumoniae isolates was done with the Quellung reaction. Serological diagnosis was assessed for 9 serotypes using World Health Organization–validated IgG and IgA serotype-specific enzyme-linked immunosorbent assays (ELISAs).
Paired admission/convalescent sera from 163 children were evaluated by ELISA (35 with proven P-CAP and 128 with nonproven P-CAP). ELISA detected pneumococci in 82.8% of patients with proven P-CAP. The serotypes identified were the same as with the Quellung reaction in 82% and 59% of cases by IgG ELISA and IgA ELISA, respectively. Overall, ELISA identified a pneumococcal etiology in 55% of patients with nonproven P-CAP. Serotypes 1 (51.6%), 7F (19%) and 5 (15.7%) were the most frequent according to IgG ELISA.
In conclusion, the serological assay allows recognition of pneumococcal origin in 55% of CAP patients with negative culture. This assay should improve the diagnosis of P-CAP in children and could be a useful tool for future epidemiological studies on childhood CAP etiology.