Age-specific reference values for cerebrospinal fluid protein concentration in neonates and young infants

Cerebrospinal fluid (CSF) protein values decline over the first few months of life as the infant's blood-CSF barrier matures. However, published studies differ in the reported rate, timing, and magnitude of this decline.

To quantify the age-related changes in CSF protein concentration and to determine accurate, age-specific reference values for neonates and young infants.

This cross-sectional study included infants age 56 days or younger who had a lumbar puncture performed in the emergency department of an urban tertiary care children's hospital between January 1, 2005 and June 30, 2007. Infants with conditions associated with elevated CSF protein concentrations, including traumatic lumbar puncture and bacterial or viral meningitis, were excluded.

Of 1064 infants undergoing lumbar puncture, 375 (35%) met inclusion criteria. The median CSF protein value was 58 mg/dL (interquartile range: 48-72 mg/dL). In linear regression, the CSF protein concentration decreased 6.8% (95% confidence interval [CI], 5.4%-8.1%; P < 0.001) with each 1 week increase in age. The 95th percentile values were 115 mg/dL for infants ≤28 days and 89 mg/dL for infants 29-56 days. The 95th percentile values by age category were as follows: ages 0-14 days, 132 mg/dL; ages 15-28 days, 100 mg/dL; ages 29-42 days, 89 mg/dL; and ages 43-56 days, 83 mg/dL.

We quantify the age-related decline in CSF protein concentration among infants 56 days of age and younger and provide age-specific reference values. The values reported here represent the largest series to-date for this age group.