MEASURING URINARY PROTEIN WITH THE NEW BIORAD REAGENT KIT - EVALUATION AND COMPARISON WITH 5 OTHER METHODS

Total urinary protein was measured by five methods: BioRad Total Prote in Test (TPT), pyrogallol red, benzethonium chloride, sulfosalicylic a cid, trichloroacetic acid, and the results compared to those obtained by a method combining preparative ultrafiltration and the biuret react ion. TPT was linear to 1.5 g protein/l, the detection limit 0.0135 g/l , and it was 3-5 times more sensitive than the other methods. Within-d ay precision (CV) was 4.3%, (0.60 g/l), the day-to-day precision was 4 .5%. The protein contents of 35 selected urine samples assigned to one of five groups according to their electrophoretic pattern were assaye d by the five methods. No method accurately measured physiological pro teinuria, but the values for light chain (Bence Jones), glomerular, tu bular and overload proteinurias measured by TPT did not differ signifi cantly from the biuret value. The other methods differed significantly for at least three groups. Alpha 1 acid glycoprotein slightly inhibit ed TPT, but peptones, amino acids, antibiotics or normal urine constit uents had little or no effect. The TPT method has been automated (Kone Progress); normal 23-h urinary protein excretion was 36 mg/day (range 12-114), the protein creatinine ratio was 34 mg/g (12-106 mg/g).