Urinary albumin determination by the immediate bromcresol green method

Area of Science:

• Clinical Chemistry
• Analytical Biochemistry

Background:

• The bromcresol green (BCG) reagent reacts with serum proteins in two distinct phases: an immediate reaction primarily due to albumin and a slow reaction from other proteins.
• Accurate quantification of urinary albumin is crucial for diagnosing and monitoring kidney diseases, particularly in patients with proteinuria.

Purpose of the Study:

• To adapt and validate the immediate BCG reaction for the precise determination of urinary albumin concentration.
• To assess the accuracy and precision of the modified BCG method compared to a established technique.

Main Methods:

• A modified bromcresol green (BCG) assay was developed for urinary albumin determination, incorporating primary pH adjustment and a urine blank.
• The immediate BCG reaction was utilized, focusing on the rapid albumin-specific component.
• Results were compared against the Laurell "rocket" technique using regression analysis.

Main Results:

• The modified immediate BCG method demonstrated excellent correlation with the Laurell "rocket" technique (y = 17.2 + 1.006x, r = 0.99).
• High precision was observed, with within-day coefficients of variation (C.V. %) ranging from 0.9% to 2.7% across different albumin concentrations.
• The method proved effective for quantifying urinary albumin in patients with proteinuria.

Conclusions:

• The optimized immediate BCG reaction provides a simple, rapid, accurate, and precise method for urinary albumin determination.
• This technique is suitable for routine clinical laboratory use in assessing patients with proteinuria.
• The BCG assay offers a valuable alternative for quantifying urinary albumin levels efficiently.