Unpredictability of serious bacterial illness in febrile infants from birth to 1 month of age.

BACKGROUND A prior study (N Engl J Med. 1993; 329: 1437-1441) produced an effective screen to identify 1-to 2-month-old febrile infants (FIs) who are at low risk of having a serious bacterial illness (SBI). Because of anticipated differences in the epidemiological features of febrile illnesses, that Philadelphia protocol was not applied to FIs younger than 1 month. OBJECTIVES To describe the epidemiological features of febrile illness in neonates from birth to 1 month of age and to determine the applicability to this population of the Philadelphia screen for identifying FIs at low risk for SBI. DESIGN A 36-month consecutive cohort study. SETTING An urban pediatric emergency department. PARTICIPANTS Infants aged from 3 to 28 days old with temperatures of 38 degrees C or higher. INTERVENTIONS Following full evaluation for SBI, all FIs, pending results of bacterial cultures, were admitted to the hospital and empirically administered antibiotics. After their illnesses resolved, the medical records of all FIs were reviewed. At that time, the Philadelphia protocol (originally developed for 1- to 2-month-old FIs) was applied and retrospectively judged for safety and efficacy. RESULTS Of the 254 FIs enrolled, 32 (12.6%) had an SBI. The spectrum of bacterial and nonbacterial diseases closely approximated that described in 1- to 2-month-old FIs. When the Philadelphia protocol was applied to all 254 FIs, 109 (42.9%) would have been identified as at low risk for bacterial disease. Included in that group are 2 FIs with bacterial urinary tract infection, 2 FIs with bacteremia, and 1 FI with bacterial gastroenteritis. CONCLUSIONS The cause of febrile illnesses in neonates (infants younger than 1 month) approximates that of FIs 1 to 2 months of age. Unlike that for older 1- to 2-month-old FIs, however, the Philadelphia protocol lacks the sensitivity and negative predictive value to identify neonates at low risk for SBI.