Identification of febrile neonates unlikely to have bacterial infections

A prospective study was undertaken to evaluate the usefulness of low risk criteria for identifying febrile neonates unlikely to have bacterial infections, particularly bacteremia and meningitis. Using these criteria we wished to check whether these low risk neonates can be safely managed as inpatients under close observation but without receiving empiric antibiotic therapy.

We conducted a prospective study of 250 consecutive infants 28 days of age or less (range, 4 to 28 days) who had rectal temperatures of at least 38 degrees C. After a complete history, physical examination and sepsis workup, the 131 febrile neonates with clinical and laboratory findings indicating low risk for bacterial infections were hospitalized, closely observed and not given antibiotics. The low risk criteria used to identify these neonates included well appearance; absence of physical signs of an ear, eye or soft tissue infection; a white blood cell count of 5000 to 15,000/mm3, a neutrophil band form count of < 1500/mm3, a spun urine specimen that had < 10 white blood cells per high power field on microscopy and a C-reactive protein value of < 20 mg/l. The remaining 119 febrile neonates who did not meet the low risk criteria were hospitalized and given empiric antibiotics pending culture results.

The overall incidence of bacterial infections in the 250 febrile neonates was 16.4% (41 neonates) with bacteremia and/or meningitis occurring in 4.4% (11 neonates). Of the 131 low risk neonates only one (0.8%) had a bacterial infection (urinary tract infection) compared with 40 (33.6%) among the 119 who did not meet the criteria (P < 0.05). The negative predictive value of these criteria for excluding bacterial infections was 99.2% (95% confidence interval, 97.7% to 100%). For bacteremia and meningitis this figure became 100%. However, the positive predictive value and specificity of the criteria were too low to identify all febrile neonates with bacterial infections. Among the low risk group 58 (44.3%) were reclassified on the second or third hospital day, because of continued fever (35), poor activity (14) and white blood cell count > 15000/mm3 on a repeat blood test (9). They were given antibiotics, but only 1 had a urinary tract infection. This patient was then treated with a 7-day course of antibiotics. All low risk neonates recovered uneventfully with no relapses observed during their hospital stay or at the time of minimum 1-week outpatient follow-up visits.

By the low risk criteria a substantial number of febrile neonates at low risk for bacterial infections can be identified and managed safely as inpatients without antibiotic therapy.