Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

IV. Plasma Proteins
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values can be used, and then only as a rough estimate of
the TP. Another important consideration is that TP determinations
(refractometric or by biuret method) without
information on plasma protein electrophoresis have limited
value (see later discussion). For avian clinical practice, it
is advised that the clinician establish TP values using the
biuret method.
E . Effect of Protein Standards
Most commercial laboratories use a human standard for TP
and albumin (Alb) determinations, without validating the
method for the species of which the blood sample is submitted.
There are significant differences between TP concentrations
when different standards are used (e.g., human, bovine,
pigeon, and chicken standards), although there is a high correlation
between the results obtained with the various standards
( Lumeij et al ., 1990 ; Spano et al ., 1987,1988 ). When
a pigeon standard was used to determine serum TP concentration
(TP p ) with the biuret method, values found were significantly
higher compared to values found determined with
the biuret method using the human standard (TP h ), but there
was a high correlation ( Lumeij et al ., 1990 ):
TP 2. 94 0. 83 TP (P < 0. 0001; r 0.
93)
h
p
Spano et al . (1987, 1988) found consistently lower TP
values in chicken serum using a chicken standard compared
with a bovine standard. Because the use of a species-specific
standard for all species presented to the avian practitioner
is unrealistic and because a high correlation exists between
the results obtained with the various standards, it is recommended
that clinicians establish reference values for the various
species using the standard that is most commonly used
in commercial laboratories (i.e., the human standard).
F . Plasma Protein Electrophoresis:
Albumin/Globulin Ratio
Plasma protein electrophoresis (PPE) on cellulose acetate
membranes has been widely used in avian patients ( Lumeij,
1987e ; Lumeij and De Bruijne, 1985a ). In many laboratories,
agarose gel films are replacing cellulose acetate membranes.
A good correlation (r 0.998) exists between these
methods in human serum ( Archer and Battison, 1997 ).
Protein fractions that can be observed include Alb, α , β ,
and γ globulin. The α and β globulins (including fibrinogen)
are considered acute phase proteins, whereas the γ
fraction is elevated in chronic conditions and includes the
immunoglobulins. Often a prealbumin fraction can also be
observed ( Fig. 28-6 ). In healthy birds, the Alb fraction is
the largest protein fraction. In acute or chronic inflammatory
conditions, a rise in total protein caused by elevated
globulin fractions may occur. Often Alb concentrations are
Pre-alb. Alb. a b g
FIGURE 28-6 Densitometer scan and electrophoretic pattern on a cellulose
acetate membrane from a representative pigeon serum. Prealbumin,
albumin, α , β , and γ globulin. Reprinted with permission from Lumeij
and De Bruijne (1985a) .
decreased in these situations. The combined effect of these
changes is a decrease in the Alb/Globulin (A/G) ratio. Often
the total protein concentration is within the reference range,
whereas the A/G ratio is decreased, therefore the A/G ratio
is of greater clinical significance than the total protein concentration.
Examples of diseases with a decrease in the A/G
ratio are egg related peritonitis and chronic infectious diseases
such as aspergillosis, psittacosis, and tuberculosis. In
ducks, Liu et al. (1984) found that serum globulin increased
with the severity of pathological changes of amyloidosis and
that the globulin was also found in the amyloidotic tissue.
Protein electrophoresis can also be used to monitor response
to treatment. In liver failure, extremely low plasma protein
concentrations can occur in combination with a decreased
A/G ratio. Gastrointestinal and renal diseases can also lead
to severe hypoproteinemia. In birds, protein malnutrition
may lead to hypoproteinemia ( Leveille and Sauberlich,
1961 ). Increased TP concentrations with a normal A/G ratio
can be expected in dehydrated birds if the primary disease
did not cause hypoproteinemia. To calculate the A/G ratio,
prealbumin and Alb as determined by plasma protein electrophoresis
are combined as “ A ” and all globulin fractions
as “G ” (Figs 28-8 through 28-11 ; Lumeij, 1987e ).
In plasma of some species, the mobility of Alb in cellulose
acetate and agarose gels is less compared to the usual
patterns, as seen, for example, in chickens and pigeons.
In the cockatiel, for example, prealbumin migrates to a
position equivalent to chicken albumin, and albumin to
a position equivalent to chicken α globulins ( Fig. 28-7 ).
Tatum et al . (2000) has confirmed the diagnostic value of
PPE for a wide variety of raptor species.
Rosenthal et al. (2005a) questioned the reliability of
PPE in birds. However, they limited their study to healthy