Management of the Febrile Young Infant

Abstract

Infants ≤90 days of age with fever are frequently evaluated in the pediatric emergency department. Physical exam findings and individual laboratory investigations are not reliable to differentiate benign viral infections from serious bacterial infections in febrile infants. Clinical prediction models were developed over 25 years ago and have high sensitivity but relatively low specificity to identify bacterial infections in febrile infants. Newer laboratory investigations such as C-reactive protein (CRP) and procalcitonin (PCT) have favorable test characteristics compared to traditional laboratory studies such as a white blood cell count. These novel biomarkers have not gained widespread acceptance due to lack of robust prospectively collected data, varying thresholds to define positivity, and differing inclusion criteria across studies. However, CRP and PCT, when combined with other patient characteristics in the Step-by-Step approach have a high sensitivity for detection of serious bacterial infection. RNA biosignatures are a novel biomarker under investigation for detection of bacterial infection in febrile infants.

Diagnostic values of C-reactive protein and complete blood cell to identify invasive bacterial infection in young febrile infants

“…Young infants under the age of 3 months with fever are frequently evaluated for the risk of invasive bacterial infections (IBIs), which consists of bacteremia and/or bacterial meningitis, in the pediatric emergency department (PED). 1,2 However, reliable physical examination findings and routinely individual laboratory investigations are not currently available to help clinicians differentiate benign viral infections or a case of over-swaddling from serious bacterial infections in febrile infants. In such patients, urinary tract infections are the most common bacterial infections, 3 and the use of urinalysis is a highly noninvasive and sensitive test that can help clinicians in the PED to diagnose it.…”

Diagnostic Accuracy of Biomarkers for Early-Onset Neonatal Bacterial Infections: Evaluation of Serum Procalcitonin Reference Curves

“…CRP is synthesized mainly in the liver during the acute phase of a bacterial infection. However, the CRP level is also elevated in the presence of other diseases, such as collagen diseases, malignancies, and asphyxia, other than infectious diseases [ 8 , 9 ]. The WBC count is well known to be increased in infections, especially bacterial infections.…”

Performance of the Modified Boston and Philadelphia Criteria for Invasive Bacterial Infections

“…Newer biomarkers, including procalcitonin and C-reactive protein, have shown promise in risk stratifying infants. 5,18,28,49 The Step-By-Step Approach, using leukouria, serum procalcitonin, peripheral WBC, and C-reactive protein, had a sensitivity of 92% and specificity of 46% in a large prospective cohort of infants. 5 promise in identifying infants without acute bacterial infections but require further development before real-time clinical application.…”

“…14 Because of these challenges, strategies have been developed to stratify the risk of bacterial infections in young febrile infants. 5,[15][16][17][18] The Boston and Philadelphia criteria, 16,17 which were derived .2 decades ago, are 2 of the more commonly used tools for stratifying young infants' risk of bacterial infection. 8 Both use peripheral and CSF white blood cell counts (WBCs) and the absence of pyuria to classify an infant as being at low risk of serious bacterial infections (SBIs), including bacteremia, bacterial meningitis, and urinary tract infection (UTI).…”