Division of Comparative Pathology, Department of Pathology & Laboratory Medicine, University of Miami Miller School of Medicine, Miami, FL, USA
Summary
Serum protein electrophoresis is a well-described tool used in companion animals for the detection of paraproteinemia. In non-traditional species, this application has been greatly extended through the use to detect and monitor inflammation, giving great benefit both in health assessments and prognostication.
Introduction
Protein electrophoresis (EPH) is a diagnostic and research tool that has been widely applied to human and veterinary medicine for over 40 years.1,2 In companion animals, applications include use in the diagnosis of feline infectious peritonitis, ehrlichiosis, and lymphoproliferative disease.1 In general, there are six fractions resolved by EPH: pre-albumin and albumin and four fractions of globulins referred to as alpha 1, alpha 2, beta, and gamma. Within these fractions there are over 200 blood proteins.1
The acute phase response (APR) is the complex but often nonspecific response that occurs during tissue injury after initiation of infection, immunologic disorder, neoplasia, or trauma.3 Negative acute phase proteins (APP) include albumin which decreases during the APR. Positive proteins include haptoglobin which is generally considered minor APP and C-reactive protein and serum amyloid A which are major APP in most species. For many species used in research and for humans, commercially available ELISA and other antibody based automated assays are available to quantitate specific APP.
EPH Methodology and EPH Fractions
In veterinary laboratories, agarose electrophoresis systems are commonly used.4 Different protein fractions are separated proportional to their charge in an agarose gel (AGE). The gel can be stained, and fractions are quantitated by densitometry After placing delimits on the fractions, the actual g/dL of each fraction is determined by multiplying the result for total protein by each percent fraction. A newer method more commonplace in human laboratories is capillary zone electrophoresis where the sample is suspended in a capillary tube and the electrical current is applied. The fractions separate and are quantitated by an ultraviolet detector. Note that there are method and analyzer differences that create varied electrophoretic patterns so reference intervals specific to the laboratory and species should always be used.
Albumin Determinations and EPH
It is important to note that albumin quantitation by chemistry analyzers uses a dye, bromocresol green, which produces inaccurate results in some animal species.4 While most mammalian species do not have this issue, highly erroneous results can be obtained with non-mammalian vertebrates as the dye can bind globulins.5-8 In bird and reptiles species, as inflammation is often reflected in quite marked changes in globulin fractions, chemistry analyzer derived results should not be considered as there is no valid correction factor than can be applied.7,8 In elasmobranch species, albumin is often lacking entirely.9
EPH in Avian Species
EPH is rarely solely diagnostic of a particular disease but can be useful as a complementary test to routine CBC and chemistry testing.4,10,11 Globulin changes are consistently observed with aspergillosis, chlamydiosis, and liver disease among others.4,10-13 Notable, in African penguins, the observation of alpha 2 and beta globulin increases provides a high specificity and sensitivity in the diagnosis of aspergillosis.14 Also, following the A/G ratio can provide key prognostic value during the treatment.15
EPH in Reptiles
Electrophoresis has been utilized in a variety of turtle and tortoise species.16-17 For the most part, a prominent beta globulin fraction is observed in reptiles even with normal clinical condition. Except for albumin, assignment of fraction changes related to particular diseases is not currently available.
EPH in Small Exotic and Non-domesticated Mammals
For the most part, the utility of EPH of non-domesticated mammals follows that seen with companion animals although, when validated, the sensitivity of specific acute phase protein assays for inflammatory processes is often superior.3 It should be noted that EPH is a very good tool to aid in the diagnosis of neoplasia as well as to gauge the acute phase response in ferrets.18
References
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