“Normal” Upper Limits for CSF Protein Are Too Low

Findings suggest that laboratories should raise the upper limit of normal for total protein in cerebrospinal fluid and adjust for age.

What's the appropriate upper limit of normal (ULN) for total protein in cerebrospinal fluid (CSF)? The question is important, because mildly elevated CSF protein could trigger additional costly evaluation in patients with low probability of serious neurological illness. To address this issue, researchers at Mayo clinic reviewed CSF protein results in 633 community-dwelling adults (age range, 33–95; mean age, 71) who had routine lumbar punctures as part of a research study on aging. The ULN at Mayo is 35 mg/dL.

Findings were as follows:

Mean CSF protein was 52 mg/dL.
The range was 14 mg/dL to 148 mg/dL (95% reference interval, 24–93 mg/dL).
Most participants (84%) had levels above Mayo Clinic's ULN.
Mean levels varied by age — from 44 mg/dL (age …

Reviewing Author

Allan S. Brett, MD

Disclosures

Nothing to disclose

Allan S. Brett, MD

Disclosures

Nothing to disclose

“Normal” Upper Limits for CSF Protein Are Too Low

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Reviewing Author