News : 2017 : May

Case of the Month: Is It Really Albumin?

The Case of Methods to Quantitate Albumin, Dr. Carolyn Cray presents the new Case of the Month. In many species – especially birds and reptiles – the albumin value that is obtained from chemistry analyzers is not valid. Electrophoresis provides a valid albumin as well as a reflection of any ongoing acute phase responses

As the most abundant protein in normal plasma and a key negative acute phase protein, there is no doubt that albumin can provide valuable information when quantitated as part of a diagnostic workup. There are two primary ways to quantitate albumin – through chemistry analyzers and via protein electrophoresis (EPH). Chemistry analyzers use the dye bromcresol green (BCG) which has been focus of many publications. While a valid method in humans, there is poor agreement between BCG albumin and EPH albumin in many mammalian species including rabbit, rat, dog, cow, pig, sheep, cat, horse, and manatee.

In birds, an overestimation of albumin levels measured by BCG was reported with examination of samples from ducks, chickens, turkeys, and pigeons. In a definitive study of samples from clinically normal and abnormal penguins, our laboratory observed that BCG also bound globulins in addition to albumin. Thus, in those penguins with an active acute phase response, the presence of high globulin fractions falsely increased BCG albumin providing the appearance of normal clinical biochemistry if only chemistry analyzer results (and not EPH) were reviewed. Similar results have been reported for turtles. Overall, EPH can provide a valid quantitation of albumin while also provide a valuable view of ongoing inflammatory and humoral immune responses.

Case 1

A 4 year old African grey parrot presented with dyspnea and changed vocalization. These clinical signs had been observed a few months earlier but resolved without treatment. The CBC was within normal limits. Biochemistry results were also within normal limits including an albumin of 1.95 g/dL. EPH showed a marked increase in beta globulins and moderate increase in gamma globulins. The albumin was 0.59 g/dL (normal limits=1.22-2.51 g/dL). Adjunct diagnostics (including antibody and galactomannan testing) were supportive of aspergillosis and the bird responded to anti-fungal treatment.

Case 2

A 1.5 year old male thin bearded dragon presented with anorexia and lethargy. A normal WBC count was observed with a monocytosis. The PCV was mildly decreased. Biochemistry results were within normal limits include an albumin of 2.25 g/dL. EPH showed a moderate increase in beta globulins. The albumin was 1.03 g/dL (normal limits = 2.0-4.1g/dL) and the A/G ratio was 0.25 (normal limits=0.4-1.1).

References

C. Cray, A. Wack, and K.L. Arheart. Invalid measurement of plasma albumin using bromcresol green methodology in penguins (Spheniscus species). Journal of Avian Medicine and Surgery 25(1):14-22, 2011.

K. Muller and L. Brunnberg. Determination of plasma albumin concentration is healthy and diseased turtles: a comparison of protein electrophoresis and bromcresol green dye-binding method. Veterinary Clinical Pathology 39(1):79-82, 2010.