Protein determination in cerebrospinal fluid by protein dye-binding assay

In this study, Coomassie brilliant blue (CBB) and pyrogallol red/molybdate (PRM) protein dye-binding assays for total protein determination in cerebro spinal fluid (CSF) are compared. Using human albumin (HA) as a protein cali brator, protein concentration in CSF samples (n = 73) ranged from 55-1960 m g/L (median: 315 mg/L) with the CBB assay, and from 95-2450 mg/L (median: 3 95 mg/L) with the PRM assay. Linear regression analysis indicated y(CBB) = 0.824x(PRM) -8 (r = 0.99). The discrepancy between the values was investiga ted by comparing the response of the two assays to different proteins. Comp ared with HA, the PRM assay showed a more uniform response to human albumin /globulin (A/G) and bovine gamma globulin (G) than did the CBB assay, but i t gave high colour yields with bovine myelin basic protein. When CSF was as sayed using A/G as a protein calibrator, agreement between the methods impr oved (y(CBB) = 0.960x(PRM) + 0 [r = 0.99]), indicating that comparability i s dictated by the choice of protein calibrator. Of the two assays studied, the PRM assay is recommended for CSF protein determination because it gives a more uniform and linear response to human albumin and globulin over a wi der working range.