Measurement of albumin in paired cerebrospinal fluid and serum samples for the assessment of albumin quotient and intrathecal immunoglobulin synthesis

Overview

Objective: comparison of multiple methods of albumin determination in CSF and serum for the purpose of the calculation of albumin quotient (Q ALB) and intrathecal (ith.) IgG synthesis.

Design: prospective study.

Material and Methods: In selected samples, albumin and IgG in CSF and serum were determined by multiple methods and a comparison was made among methods for Q ALB and ith. IgG synthesis calculation as well. In 226 consecutive samples, ith. IgG synthesis calculation was compared with the result of oligoclonal IgG detection.

Results: Determination of serum albumin by a bromocresol green (BCG) method has been identified as the main cause of positive ith. IgG synthesis calculation. This method gave significantly higher values compared to immunoturbidimetry (IT), immunonephelometry (IN) or bromocresol purple (BCP). CSF and serum albumin concentrations measured by IT in an Optilite analyzer were significantly higher compared to those obtained in an Image 800 nephelometer, yet no significant difference of the mean was observed for Q ALB. Using BCP method in serum for the calculation of Q ALB, values obtained using IN for CSF albumin were on average by 12.8% lower compared to IT. Using IN method for both CSF and serum, the number of positive significant (>10%) ith. IgG synthesis calculations decreased from 9% to 2%.

Conclusion: CSF and serum albumin determination shall be performed using the same methods on the same analyzer. In particular, BCG method for serum albumin shall not be used for the purpose of Q ALB and ith. immunoglobulin synthesis calculations.

Keywords:

albumin – immunoturbidimetry – bromocresol green – bromocresol purple – immunonephelometry – intrathecal IgG synthesis