Because normal laboratory values
depend on the diagnostic method used, the normal variation in species/breed/age
test results, etc., this article will not provide a numerical listing of values
here. For example, a normal CBC for a pediatric kitten varies from that of
a geriatric dog, and a healthy Greyhound's values may differ from that of
a healthy German Shepherd Dog. In addition, numbers have to be interpreted
as a whole; individual abnormalities do not provide a meaningful look at overall
health. (And laboratory errors do exist, so focusing on one oddity may lead
to owner stress.)
Because lab results can be affected by the medications your pet is taking
and by the timing of the test in relation to food ingestion, always ask if
your pet should eat or take his normal medication before running the test.
(Yes, it's just like when you have to have blood work done; your physician
requires some tests to be done in a fasting state, and some not.)
The normal range of values from a given test at a given laboratory will
usually be listed on the results form, so that you can see immediately what
is not in a normal range; often, results considered to be outside of the
norm will be in bold text. Your veterinarian will point out to you which
values are of concern and why. Because of the complexity and interrelationship
of these values, allow your veterinarian to interpret them for you. Guessing
a worst case scenario will just cause you preventable stress. Sometimes the
tests will need to be repeated.
Complete Blood Count (CBC)
A CBC measures the number of red blood cells, white blood cells, and platelets.
Red blood cells carry oxygen. The CBC also measures hemoglobin, which is the
part of the red blood cell that carries the oxygen. Most white blood cells
fight infection; if an animal has a high white cell count, the pet may have
an infection. The platelet count is important because platelets help make
blood clot properly.
Albumin
Albumin is protein created in the liver. Abnormally low ranges are seen
with diseased livers, gastrointestinal disease, etc. The only time albumin
is increased is when the animal is dehydrated. Albumin helps keep the liquid
part (plasma) of the blood from migrating out of the blood vessels and into
the surrounding tissues, which would cause edema and other problems.
Alkaline Phosphatase
Alkaline phosphatase forms in body tissue. Increased levels in dogs typically
indicate liver or bone disease, or that the dog is taking prednisone. Liver
and bone disease are the most common causes for increased values in cats.
ALT
ALT is an enzyme produced in the liver, and values found in the bloodstream
increase with a diseased or damaged liver.
Amylase and Lipase
Amylase is an enzyme that is produced by the pancreas and the intestinal
tract. It helps break down sugar. Lipase is an enzyme that helps break down
fats. Pancreatitis or cancer of the liver can raise the value of both of these
enzymes.
Bile Acids
Bile acids help break down fat. Because these acids are produced in the
liver, a bile acid test evaluates both the liver itself and the blood flow
to it. Typically, bile acid tests are run pre-prandially (before eating),
and post-prandially (two hours after eating).
Bilirubin
In the liver, bilirubin is created from old red blood cells. It leaves the
body in urine and stool. Values can be elevated in pets with liver or gallbladder
disease, or in those animals whose red blood cells are being destroyed faster
than normal. Pets with elevated bilirubin can appear jaundiced (abnormal yellow
skin color).
Blood Urea Nitrogen (BUN)
BUN is a waste product. A low BUN can indicate liver disease, and an increased
BUN can indicate severe kidney disease or dehydration.
Calcium
Typically, high blood calcium is associated with cancer, but there are other
causes, such as kidney failure, bone disease, or poisoning from rodent bait.
Low blood calcium can occur just before giving birth or even during nursing
(eclampsia), problems with the parathyroid gland, or poisoning from antifreeze.
Cholesterol
As it is in people, cholesterol is a fat. Unlike in people, it doesn't contribute
to heart disease in dogs and cats. Increased cholesterol is less common in
cats than in dogs. Several diseases (diabetes, hypothyroidism, Cushing’s,
or kidney disease) can elevate cholesterol levels.
Creatinine
Creatinine is produced in the muscles and leaves the body in the urine.
Elevated values indicate kidney disease or dehydration.
Creatinine Kinase (CK)
Damaged muscles produce creatinine kinase, which goes into the bloodstream.
High values indicate problems with muscle, possibly including the heart.
Glucose
Diabetes is a typical cause of elevated glucose, which is blood sugar. Dogs
with Cushing’s disease may also have elevated levels. If the glucose has been
high for a while, it can be found both in the blood and urine. Low glucose
levels may indicate a body-wide bacterial infection (sepsis) or pancreatic
cancer; seizures are sometimes seen with low glucose.
Phosphorus
Phosphorus may be high in pets that have chronic, serious kidney disease.
Potassium
Acute kidney failure can increase levels of potassium in the bloodstream.
Sodium
Low sodium levels are commonly seen in Addison’s disease. Dehydration can
cause slightly elevated levels of sodium.
Total Protein
Total protein is a value that includes albumin plus larger proteins (globulins).
Total protein can be increased from dehydration or activity of the immune
system; like albumin, values can decrease due to liver disease.
Urinalysis
While we sometimes think of it just for urinary tract infections, urine
tests can provide diagnostic information about a number of diseases. How
urine is collected for this test may depend on what disease is suspected.
Urine can be caught in a cup during urination or by placing a needle directly
into the bladder (cystocentesis, which isn't as bad as it sounds), or even
with a catheter.
Remember, sometimes lab results are faulty. If you find several elevated
or decreased values, but your pet acts as though illness is not an issue,
there could be problems with the tests and they may need to be repeated –
after all, who are you most likely to believe, a dog who is running around
normally and thinks he’s healthy or scary lab numbers? If your pet acts normal
but the values are odd, it's usually better to repeats the tests and eliminate
all doubt about the results than to medicate a healthy animal.
Copyright 2004 - 2008 by the Veterinary Information
Network, Inc. All rights reserved.
This work was originally published by Veterinary Information
Network, Inc. (VIN) and is republished with VIN's permission.
The above information is simply informational. It's intent is not
to replace the advice of a veterinarian nor to assist you in making a diagnosis
of your pet. Please consult with your own veterinarian for confirmation of
any diagnosis. Your pets life may depend on it.
