New Lab-Based, ER Protocol Cuts Invasive Procedures in Febrile Infants

A prediction rule can identify febrile infants at low risk for serious blood infections (SBIs) using urinalysis, absolute neutrophil count (ANC), and procalcitonin levels, according to a study published Feb. 18 in JAMA Pediatrics. The authors say the protocol can both standardize care and potentially cut the need for lumbar punctures, unnecessary antibiotics, and hospitalizations, which have traditionally been included in diagnostic workups due to the serious consequences of a missed SBI (e.g., bacteremia and meningitis) in infants.

The researchers from the Pediatric Emergency Care Applied Research Network developed and validated the prediction rule to identify febrile infants (60 days and younger) at low risk for SBIs presenting at 26 emergency departments (between March 2011 and May 2013) All infants had blood and urine cultures, while cerebrospinal fluid testing was performed at the discretion of the treating clinician. A urinary tract infection (UTI) was defined as the growth of a single urine pathogen with at least 1,000 cfu/mL for cultures obtained by suprapubic aspiration, at least 50,000 cfu/mL from catheterized specimens, or 10,000 to 50,000 cfu/mL from catheterized specimens in association with an abnormal urinalysis. From the 1,821 infants, 908 were randomized to the development cohort and 913 to the validation cohort (mean age, 36 days; 42 percent girls; 43 percent white; 20 percent black; and 29 percent Hispanic).

The researchers found that SBIs were present in 9.3 percent of all infants, including 1.4 percent with bacteremia, 8.3 percent with UTIs, 0.5 percent with bacterial meningitis; and 0.9 percent with concurrent SBIs. In the development cohort, the prediction rule identified infants at low risk of SBI using a negative urinalysis result, an ANC of 4090/μL or less, and serum procalcitonin of 1.71 ng/mL or less. When applied to the validation cohort, the rule had sensitivity of 97.7 percent, specificity of 60.0 percent, negative predictive value of 99.6 percent, and negative likelihood ratio of 0.04. Across both cohorts, one infant with bacteremia and two infants with UTIs were misclassified, but no patients with bacterial meningitis were missed by the rule.

The rule's performance was nearly identical when only bacteremia and/or bacterial meningitis was included. Neither the addition of clinician suspicion nor the Yale Observation Scale score significantly improved the rule. Rounding the numerical thresholds of the ANC (4000/μL) and serum procalcitonin  (0.5 ng/mL) to easier-to-apply numbers also resulted in nearly identical model test characteristics.

Takeaway: With further validation, use of prediction rule based on standard laboratory tests can potentially decrease the use of lumbar punctures, broad-spectrum antibiotics, and hospitalization for many febrile infants 60 days and younger.