Risk of serious bacterial infection in isolated and unsuspected neutropenia.

OBJECTIVES The objective was to determine the risk of serious bacterial infection (SBI) among children without underlying risk factors for SBI who present to the emergency department (ED) for evaluation and have unsuspected and isolated neutropenia. METHODS This was a retrospective consecutive chart review from October 1995 through September 2003. All patients aged 0-21 years presenting to the ED of an urban tertiary children's hospital, who were documented to have neutropenia (defined as an absolute neutrophil count [ANC] of <1,000 cells/microL) without known underlying risk factor for SBI were eligible for inclusion. SBI was defined as growth of a pathogen from culture of blood, urine, or cerebrospinal fluid (CSF). RESULTS There were 3,179 children with an ANC of <1,000/microL during the study period. Of these, 1,888 had no underlying immunodeficiency or central venous catheter (CVC). Fifteen of 453 (3.3%; 95% confidence interval [CI] = 1.9% to 5.4%) infants less than 3 months of age had SBI: seven with bacteremia, four with meningitis, and eight with urinary tract infections. SBI was rare among children over 3 months of age (18 of 1,435; 1.3%; 95% CI = 0.7% to 2.0%): one had bacteremia, none had meningitis, and 13 had urinary tract infections. CONCLUSIONS Children older than 3 months of age without underlying immunodeficiency or CVC presenting to the ED and unexpectedly found to have isolated neutropenia are not at high risk of SBI. Infants less than 3 months of age have similar risk of SBI as febrile infants of same age.