Measuring urinary protein with the new BioRad reagent kit: evaluation and comparison with five other methods

Area of Science:

• Clinical Chemistry
• Biochemistry
• Urine Analysis

Background:

• Accurate quantification of total urinary protein is crucial for diagnosing and monitoring kidney diseases.
• Existing protein measurement methods exhibit varying sensitivities and specificities, necessitating evaluation of novel techniques.

Purpose of the Study:

• To compare the performance of the BioRad Total Protein Test (TPT) against four other common urinary protein assays.
• To evaluate the accuracy of TPT in quantifying different types of proteinuria.

Main Methods:

• Five methods for total urinary protein measurement were compared: BioRad TPT, pyrogallol red, benzethonium chloride, sulfosalicylic acid, and trichloroacetic acid.
• Results were benchmarked against a reference method combining preparative ultrafiltration and the biuret reaction.
• Urine samples from 35 patients with diverse electrophoretic patterns were analyzed.

Main Results:

• BioRad TPT demonstrated higher sensitivity (3-5 times) and linearity up to 1.5 g/l, with a low detection limit of 0.0135 g/l.
• TPT exhibited good within-day (4.3%) and day-to-day (4.5%) precision.
• TPT accurately measured light chain, glomerular, tubular, and overload proteinurias, with no significant difference from the biuret reference method, unlike other assays.

Conclusions:

• The BioRad TPT is a sensitive and precise method for total urinary protein quantification.
• TPT shows good accuracy across various proteinuria types, making it a reliable diagnostic tool.
• The automated Kone Progress system offers a practical application of the TPT method for routine clinical use.