Philadelphia Criteria in Febrile Infants

Identify febrile infants aged 29 – 56 days old who are lower risk for serious bacterial infection


The Philadelphia criteria are a list of historical, examination, and laboratory features that if all are present are reassuring to clinicians treating febrile infants aged 29-56 days. Specifically, they stratify infants into low or high-risk categories for presence of serious bacterial infection (SBI) and propose discharge (without antibiotics) and close follow-up for all low-risk children.

The Philadelphia study (Baker et al. 1992) studied 747 febrile infants aged 29-56 days old presenting to the emergency department for assessment. Patients were stratified according to the now deemed “Philadelphia criteria” into low and high-risk categories. Infants that failed one or more high-risk variables were admitted with empiric antibiotics automatically (460/747) and 14% had SBI upon return of cultures. Infants that satisfied all of the low risk criteria were randomly divided into two groups: discharge home without antibiotics with 24 and 48-hour follow up (139/747) and admission without antibiotics (148/747). Only 1 patient in all of the low-risk patients found to have SBI after return of cultures.

The Philadelphia criteria had a sensitivity of 98% (95% CI 92-100) for identifying SBI, and specificity of 42% (95% CI 38-46). This study supports the use of the Philadelphia criteria for the identification of febrile infants at low-risk for SBI and recommends they be discharged without antibiotics though with close follow up at 24 and 48 hours.

Other similar criteria often employed for febrile infants includes the Boston criteria [QxMD link to “Boston Criteria”] and the Rochester Criteria [QxMD link to the “Rochester Criteria”].

A score is assigned by the following variables.

  • Age ≥ 29 days and < 57 days
  • Rectal temperature ≥ 38.2 degrees Celsius in Emergency Department
  • Well appearing infant
  • Reassuring examination
  • Reassuring investigation parameters including:
    • WBC < 15,000 mm³
    • Band to Neutrophil ratio < 0.2
    • Urinalysis < 10 WBC / hpf
    • Urine Gram Stain negative
    • CSF < 8 WBC / mm³
    • CSF Gram Stain Negative
    • Chest X-ray has no infiltrate (if obtained)
    • Stool without blood and few to no fecal leukocytes on smear (if indicated)

Philadelphia Score = Sum of points for each variable

All reassuring findings are present (if yes to all questions)

  • Low Risk for SBI. The Philadelphia criteria have a 98% sensitivity for identifying febrile infants with SBI, with a specificity of 42%

Non-reassuring findings are present (if no to any one question)

  • Higher Risk for SBI. The Philadelphia criteria have a 98% sensitivity for identifying febrile infants with SBI, with a specificity of 42%. In the Philadelphia trial, all “Higher Risk” infants who screened positive were admitted with empiric antibiotics


Baker M.D., Bell L.M., Avner J.R.

New England Journal of Medicine 1993 November 11, 329 (20): 1437-41

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1. Age ≥ 29 days and < 57 days

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