Detection of pneumococcal capsular antigen in saliva of children with pneumonia

The concentration of pneumococcal capsular antigen (PCA) in saliva was exam ined in 44 Thai children aged between 2 months and 2 years admitted with co mmunity-acquired pneumonia and in 52 healthy controls. None of the children with pneumonia had a positive blood culture. PCA was detected by latex agg lutination in the saliva of 12/44 (27%) children with pneumonia compared wi th 9/52 (17%) of the controls. More cases than controls had a PCA titre gre ater than or equal to 10 (9/44 (20%) vs 1/52 (2%), p < 0.01). Three of the five cases with a saliva PCA titre greater than or equal to 1000 were urine PCA antigen-positive. The salivary PCA titres were higher, but not signifi cantly, in children with heavier pneumococcal carriage. Quantitative measur ement of PCA in the saliva may be valuable in helping to make an aetiologic al diagnosis in children with pneumonia.