CSF Protein (Measured) (mg/dL) | |
Serum Protein (Measured) (gram/dL) | |
Hematocrit (%) | |
CSF RBC's (Measured) (/mm^3 ) | |
Blood RBC's (x 10^6/mm^3) | |
When performing a Lumbar Puncture (LP) to obtain Cerebrospinal Fluid (CSF); it is not uncommon for some peripheral blood to mix with (contaminate) the CSF that is obtained.
In such cases, the actual protein level in the CSF can be corrected by factoring in the effect of contamination and deducting the quantity of protein present is due to contamination with peripheral blood.
The formula to correct for this is:
Corrected Protein in CSF = Measured Protein CSF - [SProt * 1000 * (100 - Hct / 100) * CSFRBC / BRBC]
Corrected and Measured Protein in CSF are both in mg/dL
SProt = Serum protein in grams/dL
Hct = Hematocrit in %
CSFRBC = RBC-s found in CSF/mm3
BRBC = RBC-s in peripheral blood in cells/mm3
As an example to demonstrate implementation of this formula, a patient has the following:
In the example above, the math is:
Corrected Protein = 30-[8 * 1000 * ( 100-38/100) * 5,000/4,000,000] = 23.8 mg/dL