Automated determination of urine and cerebrospinal fluid proteins with Coomassie Brilliant Blue and the Abbott ABA-100.

We have evaluated the use of Coomassie Brilliant Blue (CBB) dye to measure the protein of urine and cerebral spinal fluid. The method was automated and compared with the turbidimetric method and with Ponceau S dye. With both the manual and automated procedures the CBB method could be used to protein concentrations of 160 mg/dl. Comparing this method to the method measuring the turbidity produced by trichloracetic acid (TCA) we found a correlation coefficient (r) of 0.96. The regression line was CBB = 0.84 TCA + 4.97. A similar comparison to the method using Ponceau S (PS) produced an r = 0.98 and the regression line, CBB = 0.91 P-S + 3.2. The CBB method was not as affected by turbidity in the samples or by xanthochromia as was the TCA Method. It is simpler to perform than the P-S method, since it does not require decantation. With the manual method, the coefficient of variation (CV) at 40 mg/dl for within-day determinations was less than 2% and, for between-day determinations, less than 4%. While the CV was somewhat higher with the ABA than with the manual method at 40 mg/dl, it was below 5% for both within-day and between-day determinations at the concentrations between 70 and 170 mg/dl. The method using CBB is useful as both a manual and automated procedure to measure protein in urine and cerebral spinal fluid.