Significance of extreme leukocytosis in the evaluation of febrile children

Abstract

Background: 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 25,000/mm 3 , has not been well-studied. Objective: 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 3 ). Methods: A retrospective case-control study of children 2‐24 months of age was performed. Those with EL were frequency ageand gender-matched to controls with LK. Results: 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. Conclusion: Young febrile children whose emergency department evaluation revealed EL had diagnoses and rates of serious bacterial infection similar to those of children with LK.