Urine protein concentration estimation for biomarker discovery

Area of Science:

• Clinical Chemistry
• Proteomics
• Renal Medicine

Background:

• Urinary proteomics shows promise for diagnosing renal disease and pre-eclampsia.
• Accurate quantification of urinary protein is essential for these diagnostic applications.
• Existing protein assays vary in their accuracy and reliability.

Purpose of the Study:

• To compare the accuracy of common protein assays (Bicinchoninic acid (BCA), Lowry, Bradford) against a gold standard amino-acid assay.
• To evaluate assay performance in urine samples from pregnant and non-pregnant women, including those with pre-eclampsia.

Main Methods:

• Urine samples from 43 women (8 non-pregnant, 34 pregnant, 8 with pre-eclampsia) were analyzed.
• Protein concentrations were measured using Bicinchoninic acid (BCA), Lowry, and Bradford assays.
• Results were compared against an amino-acid assay as the reference standard.

Main Results:

• The Bicinchoninic acid (BCA) assay demonstrated superior performance compared to Lowry and Bradford assays.
• BCA assay showed minimal bias (0.08) when compared to the amino-acid assay.
• The amino-acid assay exhibited poor performance, especially at higher protein concentrations.

Conclusions:

• The Bicinchoninic acid (BCA) assay is a reliable method for estimating unprocessed urine protein.
• Amino-acid or BCA assays are recommended for accurate urinary protein quantification in clinical settings.
• Assay selection is critical for reliable proteomic diagnostics in renal disease and pre-eclampsia.