Effect of aggregates on albumin standardization

Area of Science:

• Biochemistry
• Clinical Chemistry
• Analytical Chemistry

Background:

• Human albumin is a critical standard in various diagnostic assays.
• The presence of albumin aggregates (dimers, polymers) can affect measurement accuracy.
• Standardization relies on accurate quantification of albumin.

Purpose of the Study:

• To investigate the impact of albumin aggregates on quantification using different analytical methods.
• To compare the accuracy of total protein assays versus specific albumin assays in the presence of aggregates.
• To determine the prevalence of aggregates in commercial albumin preparations.

Main Methods:

• Preparation and quantification of monomer, dimer, and polymer albumin pools.
• Analysis using three total-protein methods (Biuret, Folin-Lowry, spectrophotometry) and four albumin-specific methods (dye-binding, electroimmunoassay, radial immunodiffusion, automated immunoprecipitation).
• Biuret method with monomer albumin as the reference standard.

Main Results:

• Both total-protein and albumin-specific methods yielded results for aggregated albumin that differed from Biuret values.
• Radial immunodiffusion showed the highest bias, quantifying dimer and polymer pools at only 67% and 48% of Biuret values, respectively.
• Commercial albumin preparations contained 3-34% di- and polymer content.

Conclusions:

• The presence of aggregates in human albumin standards introduces significant bias in quantification.
• Method-dependent biases highlight the need for careful selection of albumin standards and analytical techniques.
• Uncritical use of albumin preparations for standardization can lead to inaccurate clinical measurements.