Gender Difference in the Evaluation of Febrile Infants Aged ≤ 60 Days Using the High or Low Risk Criteria

Background: While the reliability of low or high-risk criteria in the evaluation of febrile infants aged ≤60 days has been well documented, there is no data on the performance of these criteria in males compared to females. Objective: To evaluate gender differences in the reliability of low or high-risk criteria to exclude serious bacterial infection (SBI) in febrile infants. Methods: Two prospective cohorts were assembled. The first included febrile infants that were hospitalized for fever evaluation, the second was comprised of febrile infants that were evaluated in the emergency department. The groups were divided by low or high risk status for SBI and the data were stratified by gender. The following criteria were used to define low risk: (1) unremarkable medical history; (2) well-appearing; (3) no focal signs of infection; (4) white blood cell count between 5000 and 15,000/mm 3 ; (5) normal urinalysis; (6) no mucoid or bloody diarrhea. SBI was defines as urinary tract infection, bacteremia, meningitis, bacterial enteritis, pneumonia, skin infection, arthritis, osteomyelitis or otitis. Results: . The two groups did not differ in background, risk or outcome measurements. Of the 1702 enrolled infants, 1001 (58.8%) were male and 701 (41.2%) were female. SBIs were found in 129 (12.9%) males compared to 78 (11.1%) females (p=0.26). The sensitivity, specificity, positive or negative predictive values of the risk criteria for males compared to females were 89.9% and 78.25% (p=0.02), 65.4% and 62.8% (p=0.275), 27.8% and 20.8% (p=0.035), 97.8% and 95.8% (p=0.063) respectively. Among the infants with a pathological urinalysis, bacterial infection was found in 92.6% of males vs. 64.4% of females (P<0.001). In a multivariable analysis male high-risk patients were two-fold more likely to have a serious bacterial infection, adjusted for all other variables. Conclusions: The defined risk criteria are more sensitive and have a significantly higher positive predictive value in males compared to females. We therefore suggest that gender can positively contribute to the management of febrile infants aged ≤60 days, especially those who are classified as high risk due to pathological urinalysis.