Risk of Bacteremia for Febrile Young Children in the Post–Haemophilus influenzae Type b Era

OBJECTIVES: To determine the risk for bacteremia, in the post-Haemophilus influenzae type b era, in a prospective cohort of well-appearing febrile children 3 to 36 months of age with no obvious source of infection; and to compare the predictive abilities of objective criteria in identification of children with occult pneumococcal bacteremia from those at risk. DESIGN: All children seen from 1993 through 1996, 3 to 36 months of age with a temperature of 39.0 degrees C or higher, no identified source of infection (except otitis media), and discharged to home were considered to be at risk for occult bacteremia and included in the study. SETTING: Urban pediatric emergency department. RESULTS: Of 199868 patient visits to the emergency department, 1911 children were considered to be at risk for occult bacteremia. Blood cultures were obtained from 9465 (79%). A total of 149 blood cultures contained pathogenic organisms, indicating a rate of occult bacteremia of 1.57% (95% confidence intervals: 1.32%-1.83%). White blood cell count and absolute neutrophil count were the best predictors for occult pneumococcal bacteremia. Using a white blood cell count cutoff value of 15 cells x 10(9)/L (sensitivity, 86%; specificity, 77%; and positive predictive value, 5.1%) would result in the treatment of approximately 19 nonbacteremic children for each bacteremic child treated. CONCLUSIONS: The prevalence of occult bacteremia in children 3 to 36 months old with temperatures of 39.0 degrees C or higher and no obvious source of infection is 1.6%. The white blood cell and absolute neutrophil counts are the most accurate predictors of occult pneumococcal bacteremia and when available should be used if presumptive antibiotic therapy is being considered.