Serum albumin assay – easy or problematic analysis?

Abstract

Serum albumin determination is an important biochemical investigation in clinical laboratories. Photometric methods using albumin binding to organic dyes – bromocresol green (BCG) or bromocresol purple (BCP) – are most commonly used. These determinations are quick, simple, and inexpensive. They are, however, associated with a number of problems. Discussions on the methodological unification and use of BCP are ongoing in human laboratory medicine. The reaction of human albumin with this dye is more specific. On the other hand, its affinity for animal albumin is significantly lower, for which reason BCG is used in veterinary medicine. However, due to the lower reaction specificity of this dye, the results are slightly overestimated as the dye reacts to a lesser extent with alpha and beta globulins. This disadvantage can be largely eliminated by reducing the incubation time to about 30 s. Another problem is the method calibration. Some laboratories use species-specific albumin as calibrators, but this is technically challenging for a laboratory that analyzes albumin of many species. We therefore recommend using a commercially available calibrator that is traceable to the European Reference Material for Specific Proteins. We consider these following principles – using BCG, shortening the incubation time to 30 s and using the mentioned calibrator – as a basic condition to obtain clinically correct and inter-laboratory comparable results.