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20-05-2012 | Legal medicine | Article

Cerebrospinal fluid reference range for neonates pinpointed


Free abstract

MedWire News: Researchers have identified cerebrospinal fluid (CSF) reference ranges for hospitalized preterm infants being evaluated for sepsis.

They found that, contrary to popular belief, CSF white blood cell (WBC) counts are not significantly different between preterm and term infants, but CSF protein levels are higher and decline more slowly with postnatal age in preterm than term infants.

While previous studies have addressed the normal reference ranges for CSF for infants presenting with suspected sepsis in the emergency room setting, these have included few preterm babies.

To address this, Lakshmi Srinivasan (The Children's Hospital of Philadelphia, USA) and team studied data that were collected prospectively as part of a multisite study of preterm (<37 weeks) and term infants aged less than 6 months. All infants underwent lumbar puncture for evaluation of suspected sepsis at a neonatal intensive care unit (NICU) between March 2008 and December 2010.

Children with bacteremia or culture-proven meningitis were excluded, although those prescribed antibiotics but with unknown meningitis status were included.

Overall, 47% of the 318 infants included in the study were preterm, 62% were 7 days old or younger, 81% were 28 days old or younger, and 72% were receiving antibiotics at the time they underwent lumbar puncture.

CSF WBC did not decline significantly with increasing postnatal age in either preterm infants or term infants.

CSF protein values were significantly higher in the preterm infants compared with term infants, at median values of 104 mg/dL versus 74 mg/dL. This difference persisted when the infants were analyzed beyond the first week of life.

CSF protein values also decreased significantly with increasing postnatal age in preterm and term infants, from 120 mg/dL at birth to 50 mg/dL at 150 days, and 90 mg/dL to 40 mg/dL at 80 days, respectively.

CSF glucose levels did not differ significantly between term and preterm infants.

Further analysis revealed that antibiotic exposure did not significantly affect CSF WBC, protein, or glucose values.

"Our study is novel in that nearly half of the included infants were preterm, and a substantial proportion was receiving antibiotic therapy at the time of lumbar puncture," remark the authors.

"We found that, contrary to popular teaching, CSF WBC counts do not differ between preterm and term infants."

Srinivasan et al say that in terms of the upper and lower limits of the reference range, the use of the 95th or fifth percentile generally is acceptable for normally distributed data. However, they add, in the presence of skewed data, reference ranges defined by the interquartile range are widely accepted as the best method of presentation.

"Depending on the degree of suspicion for infection, the clinician may choose to use one or other as a cutoff," they add in The Journal of Pediatrics.

By Piriya Mahendra

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