Evaluation of the Coomassie Brilliant Blue G-250 method for urinary protein

The Coomassie Brilliant Blue G-250 method for protein in urine has been evaluated for analytical accuracy and clinical applicability. Extremely simple to perform, the test exhibits good precision and sensitivity. The color developed per gram of protein is protein-type dependent, so no single protein standard is completely satisfactory. Color intensity is linearly related to concentration up to 1500 mg/L when used with a manual bichromatic method. Accuracy was clinically acceptable for patients with a variety of protein-losing diseases, and for patients having received renal transplants; however, the method underestimates urinary light-chain proteins. In athletes and premature neonates, we observed increased protein excretion during periods of stress. The upper reference limit for protein excretion in healthy adults is about 120 mg/24 h.