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Principal Reason for Performing the Test
As an indicator of hepatic and/or biliary disease.
Most Common Abnormality Indicated by the Test
Obstructive changes in the biliary system. A special consideration for interpreting ALKP changes in
the dog is required because there are “induced” forms of ALKP due to glucocorticoids and other
influences that are not associated with the natural tissue sources of ALKP. The nonhepatic sources
of ALKP (bone, intestinal, placental) in the dog will only rarely be measured as high as threefold
above the high end of the reference range because of their relative short half-lives compared to
the induced and hepatic forms of ALKP. With both the induced and hepatic source (cholestasis) of
ALKP, serum enzyme activities are commonly greater than the threefold increase; therefore, when a
greater than threefold increase is noted in ALKP in the dog, either cholestasis or induced enzyme is
suspected.
Sample Type and Precautions
Remove plasma or serum promptly from the cells or clot. If plasma is being collected, use
only lithium heparinized samples. Hemolyzed specimens should not be used because ALKP
contamination from red blood cells will increase results while hemoglobin decreases results. Above
normal total bilirubin levels may reduce ALKP results.
Complementary Tests
Alkaline phosphatase activity is usually determined in conjunction with other tests of hepatic
function and damage.
Reaction Sequence
Ammonia (NH
3
)
Ammonia is the catabolic product of protein digestion and is extremely toxic. It is converted rapidly
in the liver to urea, which is eliminated from the body by the kidneys.
Principal Reason for Performing the Test
To evaluate hepatic function.
Most Common Abnormality Indicated by the Test
Increased ammonia—decreased hepatic functional mass or hepatic vascular shunt.
Sample Type and Precautions
Use only lithium heparinized samples.
Blood should be processed and centrifuged immediately following collection; for this reason,
plasma is recommended as the sample of choice.
Ammonia measurements in either plasma or serum are significantly affected by environmental
factors and/or the passage of time.
Minimal exposure of the sample to the air is essential.
All sample containers should be capped unless sample is being introduced or withdrawn. Do not
attempt to measure ammonia in hemolyzed samples. Contamination from the red blood cells will
invalidate the test.
Appendices
