Laser nephelometric quantitation of protein in urine and cerebrospinal fluid

We describe a rapid method for the routine determination of protein in cerebrospinal fluid (CSF) and in urine using laser nephelometer. The relative light scattering (RLS) resulting from the interaction of trichloroacetic acid (TCA) and protein is linearly related to the concentration of protein from 0.01 to 6.0 g/L. Precision studies indicate that the day-to-day coefficient of variation (CV) for two CSF controls (0.32 and 0.64 g/L) were 6.4% and 4.9%, respectively. The day-to-day CV's for two urine controls (0.39 and 0.84 g/L) were 5.8% and 2.9%, respectively. Correlation studies with a manual spectroturbidimetric method revealed a correlation coefficient of 0.99 for both CSF and urine specimens. The proposed method, which uses a smaller sample size, is fast and provides greater sensitivity at low ranges due to the ability to increase the sensitivity by the laser nephelometer.