مقایسه سطح آنتی‌بادی پنومولیزین سرمی و آنتی‌ژن پنوموکک ادراری (بیناکس) در کودکان مبتلا به عفونت تنفسی فوقانی و کودکان سالم

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 (95%CI 0.86-0.97, p<0.0001) and had 87% sensitivity and 82% specificity for differentiation between cases and controls. Conclusions: The high pneumolysin antibody level in cases with URTI strongly indicates the pneumococcal infection. Pneumolysin antibody level even in little amounts (525pg/ml) with 87% sensitivity and 82% specificity is a suitable test for diagnosis of pneumococcal infection in children with URTI, but this test should be added to conventional culture (gold standard) and rapid urinary antigen test.