This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
A baby under 3 months with a rectal temperature of 100.4 °F (38 °C) or more needs to be seen by a doctor the same day.
The problem of fever in young infants
Most febrile infants have a viral infection, but in the first two months of life about 1 in 10 has a serious bacterial infection, most often a urinary tract infection, sometimes bacteremia or meningitis. Young infants show few specific signs, so doctors long performed a full evaluation, including a lumbar puncture, admission and antibiotics, for every febrile baby. Decision rules were developed to identify infants at low risk who could be managed more gently.
The Rochester criteria
Developed at the University of Rochester and published by Dagan and colleagues in 1985, then validated in 1994, the criteria apply to infants 60 days old or younger with a fever of 38 °C (100.4 °F) or more. An infant is at low risk if all of these are true:
- appears generally well;
- previously healthy: born at term (37 weeks or more), no perinatal antibiotics, not treated for unexplained jaundice, no previous antibiotics or hospital stay, no chronic illness, not kept in hospital longer than the mother;
- no focal infection of the skin, soft tissue, bone, joint or ear;
- white blood cell count between 5 and 15 × 10⁹/L;
- absolute band count of 1,500/mm³ or less;
- urine: 10 white cells or fewer per high-power field;
- stool, if there is diarrhea: 5 white cells or fewer per high-power field.
Performance
In the 1994 validation study, about 1% of low-risk infants had a serious bacterial infection. The criteria were good at identifying low-risk infants but did not perform as well in the first month of life.
Current practice
Newer approaches combine age, urinalysis and inflammatory markers:
- the 2021 American Academy of Pediatrics guideline for well-appearing febrile infants aged 8 to 60 days;
- the PECARN rule, using urinalysis, neutrophil count and procalcitonin;
- the European Step-by-Step approach.
Infants 21 days old or younger are generally evaluated fully and treated regardless of risk criteria.
Example
A 30-day-old infant who looks well, was born at term, has no focal infection, a white count of 11 × 10⁹/L, 800 bands/mm³ and 3 white cells per field in the urine meets all the criteria: low risk. Management still depends on the clinician, local guidelines and the family’s ability to return quickly.