Risk Factors of Serious Bacterial Infection in Previously Healthy Children Older Than 90 Days Old With Fever and Neutropenia.

Background: The main objective was to determine the clinical or analytical factors that independently predict risk of serious bacterial infection (RSBI) in immunocompetent patients older than 90 days given a diagnosis of fever and for whom neutropenia was an incidental finding. The secondary objective was to describe the prevalence of serious bacterial infections (SBIs).

Methods: This is a 3-year-long, multicenter, prospective analytical and observational study carried out at 6 pediatric emergency departments. Data for epidemiological, clinical, and analytical variables were collected.

Results: One hundred forty patients with febrile neutropenia (60.7% mild, 39.3% moderate to severe) were recruited. Serious bacterial infection incidence was 15.0% (95% confidence interval [CI], 9-21): 1 Invasive Bacterial Infection (Staphylococcus epidermidis bacteremia), 10 urinary tract infections, 8 pneumonias, and 2 cellulitis. Median total neutrophil counts per microliter showed no statistically significant differences (P = 0.512; 1000 [750-1200] in SBI patients vs 1100 [800-1300] in non-SBI patients). Higher RSBI was observed in patients with neutrophils less than 20% relative to total leukocytes (SBI, 15, 26.3%) than in those with neutrophils of 20% or greater (SBI, 6, 7.2%) (odds ratio, 4.6; 95% CI, 1.7-12.7). In patients with greater than 5000 leukocytes/μL, a percentage of neutrophils less than 20% was related to a greater RSBI with a trend toward statistical significance (odds ratio, 6.1; 95% CI, 0.7-51.1; P = 0.066). The clinical variables did not show a significant association with RSBI.

Conclusions: None of the clinical or analytical variables assessed were associated with the RSBI. However, according to a post hoc analysis, in patients with greater than 5000 leukocytes/μL, a neutrophil percentage less than 20% could be an independent risk factor for SBI. A thorough physical examination and basic diagnostic tests (urinalysis and chest x-ray) may help to establish a diagnosis of SBI in the vast majority of cases.