CSF-to-Serum Albumin Index and the Intactness of the Blood-Brain Barrier

CSF-to-serum albumin index =

= (CSF albumin in mg/dL) / (serum albumin in g/dL)

Interpretation:

• The normal range is 4-8; if the CSF albumin is expressed in g/dL, the normal value is 0.004-0.008

• values of 9-14 indicate slight impairment in the blood-brain barrier

• values of 15-30 indicate moderate impairment

• values over 30 indicate severe impairment

• values reach adult levels at about 6 months; younger infants have slightly elevated values reflecting immaturity of the barrier

• values tend to increase slowly after age 40

Limitations:

• A traumatic CSF tap results in a false elevation of the index.