Cerebrospinal Fluid Protein Concentration in Full-Term Neonates—Reply

In reply

We thank Dr Anagnostakis and colleagues for their interest in our article¹ and for presenting their comparable data on CSF protein levels in neonates. We agree with their comments about the developmentally regulated relationship between BBB permeability and CSF protein concentration. Furthermore, we would like to emphasize an important point from our study concerning CSF protein in neonates. Although several other studies have also reported that CSF protein concentration is higher in neonates than in older infants and children,^2- 4 a major conclusion from our study, which is supported by the data presented by Dr Anagnostakis and colleagues, is that CSF protein levels in "healthy" term neonates may actually not be as high as previously reported. While some studies⁴ and popular reference sources⁵ list the upper limit of normal CSF protein levels for term neonates to be as high as 1.7 g/L, our data suggest that CSF protein levels higher than 1.0 g/L in term neonates are worrisome for a pathological process. Similarly, our reference range for CSF protein concentration in preadolescent children (<0.35 g/L) is lower than that commonly reported in many previous studies and standard reference sources. We suggest that the lower reference ranges found in our study may be attributed to more stringent methods of defining the "normal" reference group, such as very strict criteria for eliminating traumatic lumbar punctures and the use of enterovirus polymerase chain reaction to exclude previously undiagnosed cases of meningitis.