Clinical Pathology Laboratory - Available Test
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Individual Chemistry Tests
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| All the chemistry tests that are components of our panels can be
ordered individually. There are also some tests that are not included
in the panel, which must be ordered as individual tests. These are
indicated below. Click on certain tests to obtain more information.
Please refer to our Chemistry Module for additional information about
the tests, including disease associations. |
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Bile acids: |
- Bile acids provide useful information
about the portal venous circulation and hepatic function.
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Cholinesterase: |
- Measurement of cholinesterase activity in serum or plasma is
a quick screening test indicated for animals with a history of
possible exposure to organophosphate or carbamate compounds and/or
that show clinical signs compatible with exposure. Remember that
erythrocytes are rich in cholinesterase, therefore hemolysis invalidates
the results.
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LDH: |
- Lactate dehydrogenase catalyzes the conversion of lactate to
pyruvate. It is not tissue-specific, being found in a variety
of tissues, including liver, heart and skeletal muscle. There
are at least 5 different isoenzymes, which are found in varying
proportions in different tissues. Because LDH is so non-specific
and isoenzyme measurement is not routinely available, its measurement
does not confer any additional information about skeletal muscle
or hepatic disease in domestic animals, than that provided by
enzyme assays routinely used for this purpose (i.e. CK for muscle
and SDH and ALT for liver).
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Lipase: |
- Lipase hydrolyzes triglycerides and is used primarily as an
indicator of pancreatitis in dogs. Lipase concentrations are variably
increased in cats with pancreatitis, so it is less useful in this
species.
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Non-essential fatty acid (NEFAs),B-hydroxybutyrate (BHBA) and metabolic
profile testing in cattle: |
- NEFAs are performed to evaluate the energy balance of prepartum
dairy cows, in particular. BHBA testing is performed to determine
the incidence of sub-clinical ketosis in dairy cows post-calving.
These tests should never be interpreted on an individual cow basis
and are only meaningful when interpreted on a herd-basis. For
this reason, we recommend a minimum of 12 samples be submitted
from each herd for this testing (these samples can be submitted
whenever suitable cows can be tested and do not have to be submitted
simultaneously - they should, however, be interpreted together).
We also offer a metabolic profile test in dairy cows post-calving.
This test includes BHBA, NEFAs, BUN, albumin and AST. We will
provide guidelines on interpretation with the test results.
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Osmolality: |
- Serum and urine osmolality is affected by the number of osmotically
active particles in solution and is unaffected by their molecular
weight and size. For this reason, osmolality is superior to specific
gravity, which is affected by particle weight and size.We measure
osmolality with a freezing point depression osmometer; 1 osmol
(defined as 1 mol of a nondissolving substance in 1 kg H2O) will
decrease the freezing point by 1.86°C. Normal serum or plasma
osmolality is between 290 and 330 mOsm/kg and is determined principally
by sodium, which together with glucose, is an effective osmol.
Urine osmolality is useful for evaluating urine concentrating
ability, e.g. water deprivation tests, and is more accurate than
measurement of urine specific gravity in this regard. Serum or
plasma osmolality provides valuable information in suspected hyperosmolar
states, e.g. hyperosmolar diabetic ketoacidosis or ethylene glycol
poisoning. In the latter condition, an osmolal gap can be calculated
from the measured osmolality minus the calculated osmolality.
A very high osmolal gap (> 25) supports a diagnosis of ethylene
glycol poisoning. Calculated osmolality is determined as follows:
Calculated osmolality = 2 x (Na + K) + (glucose ÷ 18) +
(BUN ÷ 2.8),
where values for glucose and BUN are in mg/dL and values for Na
and K are in mEq/L
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SDH: |
- Sorbitol dehydrogenase is found in highest concentration in
the liver. It is a cytoplasmic enzyme with a short half life (12-24
hours). It is a very specific indicator of liver disease in all
species, with increases occurring within 24 hours of liver injury.
SDH is the enzyme of choice for detecting hepatocellular injury
in large animals and is included in our large animal chemistry
panel.
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Triglycerides: |
- Triglycerides are found in high concentrations in chylomicrons
(CM) and very low density lipoproteins (VLDL). CM carry lipid
absorbed after eating from the GI tract for uptake by adipose
tissue and skeletal muscle. VLDL are produced in the liver from
free fatty acids and are the main carrier of triglycerides in
the fasting state, transporting triglycerides and cholesterol
from the liver to peripheral tissues. Increased triglycerides
can be seen secondary to increased CM (e.g. post-prandially) or
increased VLDL (diseases, such as pancreatitis, diabetes mellitus,
Cushing's etc). Visible lactescence (lipemia) in a blood sample
is due to increased triglycerides.
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Urinary bile acid measurement in dogs and cats: |
- Measurement of urinary bile acids (as a bile acid to creatinine
ratio) is recommended for screening dogs and cats for hepatic
insufficiency/injury and portosystemic shunts (acquired or congenital).
Small amounts of bile acids are found in the urine from healthy
animals, however if serum bile acids are increased, the excess
bile acids are excreted by the kidneys, resulting in high urinary
bile acid concentrations. High urinary bile acid concentrations
indicate the need for further hepatic testing, e.g. aspirates/biopsy,
ultrasonographic and/or radiographic imaging.
Measurement of urinary bile acid is advantageous over serum bile
acid testing (particularly random samples) as patients do not
need to be fasted and sample collection is simple.
Samples should ideally be collected from animals without any evidence
of renal disease (acute or chronic renal failure, cystitis, etc).
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Uric acid: |
- Uric acid is formed in the liver from the catabolism of the
nucleic acids, adenine and guanine. Certain dog breeds, e.g. Dalmations,
have a defect in uric acid metabolism, resulting in supersaturation
of the urine with uric acid. This predisposes this breed to urate
urolithiasis (see uric acid under our urine tests). Uric acid
is also used to assess renal function in birds (see non-mammalian
chemistry panel). It can be measured in urine or blood.
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