Evaluation of a rapid urine antigen assay for the detection of invasive pneumococcal disease in children

Objective. Streptococcus pneumoniae remains the most common cause of occult bacteremia, bacterial pneumonia, and meningitis in young febrile children. We sought to determine the utility of a pneumococcal urine antigen assay among young febrile children at varying risk of invasive pneumococcal disease. Methods. We prospectively enrolled 5 groups of children, 3 months to 5 years of age, who presented to an urban pediatric emergency department or hospital-based clinic between January 1, 2000, and April 1, 2001. The groups enrolled included 1) children with pneumococcal bacteremia, 2) febrile children with pneumonia, 3) febrile nonbacteremic children with leukocytosis, 4) febrile nonbacteremic children with normal white blood cell (WBC) counts, and 5) afebrile children with no evidence of current or recent bacterial infection. Results. Of 346 children enrolled, positive assay results were found in 23 ( 95%) of 24 with pneumococcal bacteremia ( 95% confidence interval [ CI]: 77% - 100%), 47 ( 76%) of 62 with lobar pneumonia ( 95% CI: 63% - 85%), 28 ( 15%) of 181 nonbacteremic children with fever ( 95% CI: 11% - 22%) with no difference among patients with elevated WBC counts ( 18%; 95% CI: 11% - 27%) compared with those with normal WBC counts ( 11%; 95% CI: 5% 21%), and 6 of 79 patients without fever ( 8%; 95% CI: 3% - 16%). Conclusions. This S pneumoniae antigen detection assay demonstrated high sensitivity for proven ( bacteremic) and suspected ( focal pneumonia) invasive pneumococcal infections. The rate of false- positive test results among febrile children without identified pneumococcal infection is approximately 15%. Although not ideal, this combination of sensitivity and specificity compares favorably with other available tests, such as the WBC or absolute neutrophil count used to screen children for clinically unsuspected pneumococcal infections.