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 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 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 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 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).
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).
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.
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 Kinase (CK)
Damaged muscles produce creatinine kinase, which goes into the bloodstream. High values indicate problems with muscle, possibly including the heart.
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 may be high in pets that have chronic, serious kidney disease.
Acute kidney failure can increase levels of potassium in the bloodstream.
Symmetric dimethylarginine (SDMA) is excreted primarily by the kidneys. The serum concentration of SDMA is affected by changes in the glomerular filtration rate (GFR). SDMA has been shown to be a more sensitive biomarker than serum creatinine for assessing renal dysfunction in people. Studies have shown that SDMA increases after 40 percent of kidney function is lost, and creatinine increases after 75 percent is lost. Many things can affect the SDMA numbers, so an increase in the SDMA number should be interpreted appropriately. Things that can affect the number are hydration status (dehydration, water restriction for surgery, etc.), age of the animal (young animals tend to have higher numbers than adults), medications (e.g., NSAIDs), post-renal obstruction, low blood pressure, infections, thyroid disease, etc. (Anything that decreases the kidneys’ ability to filter the blood will cause an increase in the SDMA number.)
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.
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.
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.
Adapted from: https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952533