Significance of Extreme Leukocytosis in the Evaluation of Febrile Children

Abstract

Emergency department evaluation of young febrile children often includes a white blood cell count. Although a high white blood cell count is associated with an increased likelihood of infection, the clinical significance of extreme leukocytosis (EL), defined as a white blood cell count of > or = 25,000/mm, has not been well-studied. To determine diagnoses associated with EL in febrile children evaluated in a pediatric emergency department and to compare rates of serious bacterial infection in those with EL and in those with more modest leukocytosis (LK) (15,000-24,999/mm). A retrospective case-control study of children 2-24 months of age was performed. Those with EL were frequency age- and gender-matched to controls with LK. Sixty-nine patients with EL and 94 patients with LK were included. The mean age was 9.9 months, and 91 (56%) patients were male. The diagnoses were similar between the 2 groups, with otitis media, viral syndrome and pneumonia being the most common. The rates of proven serious bacterial infection were similar between EL (25%; 95% confidence interval, 15-36%) and LK (17%; 95% confidence interval, 10-26%) patients. Using different white blood cell cutoff points did not distinguish between patients with and without serious bacterial infection. Young febrile children whose emergency department evaluation revealed EL had diagnoses and rates of serious bacterial infection similar to those of children with LK.