Bias between two methods of albumin measurement in the white rhinoceros, Ceratotherium simum

Background: The bromocresol green (BCG) method has been reported to overestimate serum albumin concentration in several species due to non-specific binding to globulins. As the white rhinoceros has high concentrations of serum globulins, significant differences in albumin measured by the BCG method, and the field method of agarose gel serum protein electrophoresis (SPE) are expected.

Objectives: We aimed to compare the BCG and SPE methods for albumin determination in the serum of white rhinoceroses.

Methods: SPE and BCG albumin were measured in 82 white rhinoceros serum samples. Results were compared using Bland-Altman difference plots and Passing-Bablok regression analysis.

Results: BCG albumin showed a significant mean constant positive bias of 7 g/L, or 36%, which was more than the total allowable error of 15% and was clinically significant. Methods were not comparable within the inherent imprecision of each method.

Conclusions: The BCG method overestimated albumin concentrations in this species compared with agarose gel SPE, and method-specific reference intervals should be used.