Purpose: Approximately 8-10% of febrile infants ≤60 days of age presenting to emergency departments (ED) have serious bacterial infections (SBI). Little is known about the risk of SBI in infants with only a history of fever but who are afebrile at ED presentation as compared to infants with a documented fever in the ED. The purpose of this study is to evaluate the risk of SBI in infants ≤60 days of age with history of fever only versus those with documented fever in the ED, using data derived from a large, prospective cohort. Methods: We performed a secondary data analysis from a multicenter prospective study of infants ≤60 days of age evaluated for SBIs between December 2008 and May 2013 at 26 pediatric EDs. We compared rates of SBI (defined as urinary tract infection [UTI], bacteremia and/or bacterial meningitis) between infants with a history of fever alone versus those with documented fever (rectal temperature ≥38.0°C) at the time of ED evaluation. Bacteremia and meningitis were defined as growth of a known pathogen from blood and CSF cultures, respectively. UTI was defined using pre-specified criteria from results of urinalysis and urine culture. We performed subanalyses by age group (≤28 days vs 29-60 days) and by type of SBI. We report relative risks (RR) with 95% confidence intervals (CI) between groups. Results: 3,821 infants were included, of whom 1,654 (43.3%) were girls; the mean age was 35.1 days (SD 14.7) (Figure). Of 1,243/3,821 (32.5%) infants afebrile in the ED, 111/1,243 (8.9%) had SBIs. Of 2,578/3,821 (67.5%) infants febrile in the ED, 327/2578 (12.7%) had SBIs. RR for any SBI for afebrile versus febrile patients was 0.70 (95% CI 0.57-0.86). An overall lower risk of any SBI was also seen among afebrile infants ≤28 days of age (RR 0.67, 95% CI 0.50-0.91) and 29-60 days of age (RR 0.73, 95% CI 0.55-0.96) as compared to febrile infants (Table). Conclusions: The prevalence of SBI in infants ≤60 days of age with a history of fever at home but afebrile at ED presentation is lower than those who are febrile in the ED. Nevertheless, SBI rates remained substantial in the afebrile group such that the ED evaluation for these two groups should be similar.

Table

Numbers of patients in primary study and subgroup analysis with SBI with associated relative risk.

Table

Numbers of patients in primary study and subgroup analysis with SBI with associated relative risk.

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