Table 1. CBB-Measured Protein Concentrations (gIL) In Urine SpecImens Diluted to Achieve Bluret-Predicted ProteIn Concentrations

Urine SpecImens Diluted to Achieve Bluret-Predicted ProteIn Concentrations of 4 to 0.2 gIL The Coomassie Brilliant Blue (CBB) dye-binding method for determining total protein in urine is widely used in clinical laboratories because it is sensitive, easily automated, and free from interference by many clinically relevant substances (1-6). However, it yields different results for the same concentrations of different proteins (2,5-10). In clinical studies of urinary protein consisting predominantly of albumin, response curves reportedly were nearly linear for protein concentrations up to 1 gIL (2-4), but linearity for clinical specimens with mixed nonalbuminous proteins has not been established. We report here the accuracy and linearity of the CBB method for determination of urinary protein in patients with glomerular or renal tubular disease, in comparison with results obtained with the biuret method.