Isolated elevated blood neutrophil concentration at altitude does not require NICU admission if appropriate reference ranges are used

Abstract

The Intermountain Healthcare hospitals use a clinical pathway algorithm for early-onset infection, which is based on the 2002 Centers for Disease Control and Prevention (CDC) guidelines for perinatal group B streptococcal disease. As part of this pathway, neonates in the well baby nursery, who seem to be well but have risk factors for infection, receive a 'limited laboratory evaluation including a CBC', and if the complete blood cell count (CBC) is abnormal, antibiotic treatment and neonatal intensive care unit (NICU) monitoring are initiated. We recently found that reference ranges for absolute neutrophil counts (ANCs) are much wider at our altitude (4800 to 5000 ft) than at sea level. On this basis, we speculated that some well babies with risk factors for infection are mistakenly judged as having an abnormal CBC, and are unnecessarily admitted to the NICU. This was a retrospective observational cohort study of neonates of >37 weeks gestation admitted to either of two Intermountain Healthcare NICUs for intravenous antibiotic treatment during a recent 36-month period. During the study period 3217 patients were admitted to the two NICUs, 1049 (32.6%) of which were born at>37 weeks gestation. Of these, 14 (1.3%) were found to have been admitted to the NICU on the basis of an abnormal CBC (elevated ANC), when in retrospect, using the appropriate ANC chart, their CBCs were completely normal. None of the 14 neonates had a leukocyte left shift (immature to total neutrophil ratio >0.3) or thrombocytopenia. None were treated with supplemental oxygen or mechanical ventilation in the NICU. All 14 had sterile blood cultures. All had antibiotics stopped in 48 to 72 h, and all were discharged home as well babies. We identified 14 neonates who, while in the well baby nursery, were found to have risk factors for early-onset infection, but did not seem to be infected, and were subsequently admitted to a NICU for intravenous antibiotic treatment and monitoring under the mistaken impression that they had an abnormal CBC. We maintain that use of an appropriate neutrophil reference range chart can reduce NICU admissions and can limit unnecessary antibiotic exposure.