- Serious BD in febrile infants <3mo is difficult to exclude on clinical grounds. In most medical centers such infants are hospitalized and treated with broad spectrum antibiotics despite cost and iatrogenic risk. The purpose of this prospective study was to test the ability of simple, objective criteria to identify infants at LR for BD. From 7/82-11/83 all previously healthy infants <3mo hospitalized for suspected sepsis were studied. Of 168 infants, 85% were <60 days old. Their mean temp. was 38.9°C. Laboratory evaluation included: CBC; U/A; LP; culture of blood, CSF and urine for bacteria; and viral cultures. An etiologic agent was identified for 120 (72% of the 168 infants). There were 105 infants considered to be at LR for BD by the following criteria: 1) normal neonatal history; 2) no evidence of soft tissue, skeletal or ear infection; 3) normal CBC (WBC 5000-15,000/mm3, <1500 bands/mm3); 4) normal U/A. A group of 63 infants did not meet these critiera. The 2 groups did not differ in age or clinical presentation. None of the infants at LR had BD while 17 (27%) of 63 not meeting our criteria did (p<.00001). An infecting virus was identified in 70% of the infants at LR and in 59% of those not meeting our criteria (p>.05). These findings suggest that simple, objective criteria can identify a large group of infants <3mo at low risk for BD for whom treatment with antibiotics might not be indicated.