Invalid Measurement of Plasma Albumin Using Bromcresol Green Methodology in Penguins (Spheniscus species)

Abstract

The purpose of this study was to examine the validity of albumin determinations in penguin plasma by the bromcresol green (BCG) method and the gold standard of protein electrophoresis (EPH). Plasma from 96 clinically normal and abnormal penguins (Spheniscus species) was analyzed. The 2 methods did not yield equivalent results. The BCG method underestimated the albumin level in samples from normal patients (indicated by a normal albumin:globulin ratio) and overestimated the albumin level in samples from clinically abnormal penguins (indicated by a decreased albumin:globulin ratio). After EPH of plasma samples from clinically abnormal penguins samples was performed to separate albumin and globulin fractions, the globulins exhibited marked binding to the BCG dye. There were no significant differences between the variable reaction of paired serum and plasma samples when using the BCG method. These results demonstrated marked differences in the determination of albumin levels when using the BCG method and protein EPH. They further demonstrated that the BCG method can provide erroneous results, which have the potential to significantly impact clinical diagnosis and treatment. This study confirmed findings from previous studies in other avian species that the BCG method yields unreliable results in avian species. It is our conclusion that the BCG method, commonly found on automated analyzers in commercial laboratories and on point-of-care analyzers, should not be used to determine albumin concentration in avian samples.