Serum pneumolysin antibody and urinary pneumococcal antigens (binax) level in children with upper respiratory tract infection versus normal controls

Background: Streptococcus pneumoniae is a common cause of respiratory infection. Pneumococcal upper respiratory tract infection (URTI) in children is seldom bacteremic. Determination the prevalence of S.pneumoniae infections in children with URTI using rapid urinary antigen test (BINAX now) and titration of serum pneumolysin antibody (added to conventional culture) was the object of this study. Methods: A cross sectional, case-control study done in ENT & pediatric departments of Rasoul Hospital in Tehran, Iran, (2008 -2010) upon 133 cases with upper respiratory tract infection (otitis media, sinusitis and tracheitis). The nosocomial infection omitted in first step. 60 remaining cases followed for S.pneumoniae infection by culture and rapid urinary antigen test (Binax Now). Serum pneumolysin antibody titers compared between 45 cases and 66 controls. Results: Positive culture (S.pneumoniae, H.influenza) obtained in 4/60 URTI cases. Positive urinary S.pneumoniae antigen detected in 50 (30/60) of cases and 6 (4/66) of controls (p=0.01). The pneumolysin antibody level with cut-off level 525pg/ml was higher in URTI cases than controls (982±441 Vs. 525±42, p<0.0001). Area under the ROC curve for pneumolysin antibody was 0.923 (95CI 0.86-0.97, p