Accuracy of Complete Blood Cell Counts to Identify Febrile Infants 60 Days or Younger With Invasive Bacterial Infections

Abstract

IMPORTANCE Clinicians often risk stratify young febrile infants for invasive bacterial infections (IBIs), defined as bacteremia and/or bacterial meningitis, using complete blood cell count parameters.OBJECTIVE To estimate the accuracy of individual complete blood cell count parameters to identify febrile infants with IBIs. DESIGN, SETTING, AND PARTICIPANTSPlanned secondary analysis of a prospective observational cohort study comprising 26 emergency departments in the Pediatric Emergency Care Applied Research Network from 2008 to 2013. We included febrile (Ն38°C), previously healthy, full-term infants younger than 60 days for whom blood cultures were obtained. All infants had either cerebrospinal fluid cultures or 7-day follow-up. MAIN OUTCOMES AND MEASURESWe tested the accuracy of the white blood cell count, absolute neutrophil count, and platelet count at commonly used thresholds for IBIs. We determined optimal thresholds using receiver operating characteristic curves. RESULTSOf 4313 enrolled infants, 1340 (31%; 95% CI, 30% to 32%) were aged 0 to 28 days, 2412 were boys (56%), and 2471 were white (57%). Ninety-seven (2.2%; 95% CI, 1.8% to 2.7%) had IBIs. Sensitivities were low for common complete blood cell count parameter thresholds: white blood cell count less than 5000/μL, 10% (95% CI, 4% to 16%) (to convert to 10 9 per liter, multiply by 0.001); white blood cell count Ն15 000/μL, 27% (95% CI, 18% to 36%); absolute neutrophil count Ն10 000/μL, 18% (95% CI, 10% to 25%) (to convert to × 10 9 per liter, multiply by 0.001); and platelets <100 × 10 3 /μL, 7% (95% CI, 2% to 12%) (to convert to × 10 9 per liter, multiply by 1). Optimal thresholds for white blood cell count (11 600/μL), absolute neutrophil count (4100/μL), and platelet count (362 × 10 3 /μL) were identified in models that had areas under the receiver operating characteristic curves of 0.57 (95% CI, 0.50-0.63), 0.70 (95% CI, 0.64-0.76), and 0.61 (95% CI, 0.55-0.67), respectively. CONCLUSIONS AND RELEVANCENo complete blood cell count parameter at commonly used or optimal thresholds identified febrile infants 60 days or younger with IBIs with high accuracy. Better diagnostic tools are needed to risk stratify young febrile infants for IBIs.

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

“…In line with previous prospective results in young infants for IBI, 6 we found that WBC count has a poor ability to differentiate between young febrile infants with and without IBIs in PEDs. Due to the low incidence of IBIs, most abnormal WBC results are not associated with the presence of an IBI.…”

“…All patients aged 0e3 months old who visited the PED with the clinical symptom of infection or fever were included in the study, and IBIs were defined as bacteremia or bacterial meningitis. 6 All patients' vital signs at triage and laboratory tests were recorded. The primary outcome of this study was to describe the potential for IBIs in young febrile infants based on their clinical parameters.…”

“…5 Earlier this year, a large cohort study of prospectively enrolled young febrile infants uncovered that using complete blood cell count parameters or optimal thresholds does not have high accuracy in identifying febrile infants with IBIs. 6 The risk of bacteremia is higher in infants under one year old than in other age groups. Previous studies have discussed elevated C-reactive protein (CRP) levels in children with bacteremia and monitoring CRP level as an indicator of sepsis.…”

How to predict serious bacterial infections in young febrile infants in the emergency department?

“…In 2017, Cruz et al conducted a large prospective observational cohort study and found that CBC parameters had poor accuracy in distinguishing febrile infants with IBIs. 5 The possible explanation for the poor performance of CBC may be the changing epidemiology of IBIs in young infants due to the effect of immunity resulting from the use of conjugate vaccines of Haemophilus influenzae type b and Streptococcus pneumoniae and the development of screening and antibiotic prophylaxis of Group B Streptococcus. The most common pathogens of SBIs identified in the modern era is E. coli; it may produce less of an inflammatory response and less leukocytosis by the host and thus decrease the sensitivity of CBC.…”

Afebrile neonates with pustules should not be managed as febrile infants

“…Because neither clinical appearance nor individual laboratory tests can reliably identify serious bacterial infection in infants age 60 days old or younger, febrile infants evaluated in the pediatric emergency department routinely undergo urine, blood, and often cerebrospinal fluid testing, and many are hospitalized on parenteral antibiotic therapy pending bacterial culture results . The operative word that drives this practice is “febrile,” because approximately 10% of these febrile infants have a serious bacterial infection, and 2% have an invasive bacterial infection .…”