Understanding the Importance of Your Cats Bloodwork

By:  Dawn Skupin, Stedam American Shorthairs

Your cat’s blood work is a very important diagnostic tool that provides a host of information about his or her  health.  It is a great tool even when used for healthy cats as it can show small inconsistencies that could be the beginning of a health problem as well as to help clarify symptoms that the cat already is showing.  These tests also serve as a baseline for future monitoring of the cat’s health.

Whether it is a human, dog, cat, or any other mammal when sick, a doctor or veterinarian usually draws a blood sample and perform tests to help determine a diagnosis of the symptoms presented.  These tests are typically one of two types of blood work.  The first type is a complete blood count, (CBC), which determines the number and type of blood cells present; red and white cells and platelets.  The complete blood count also includes a measure of hemoglobin which is the actual substance in the red blood cell that carries the oxygen to tissues in the body.  This type of blood work is concerned with the cellular portion of the blood and is called hematology. The second type of test is called a blood or serum chemistry panel.  This measures quantities of various electrolytes, enzymes or chemical compounds in the liquid/clear portion, called plasma, of the blood sample.  This is a series of blood tests used to evaluate the function of major organs and body systems.

The results of the laboratory workup on a specific cat are compared to reference ranges established by measuring the laboratory parameters in a group of normal animals. Combined with hematology and urinalysis, the biochemical profile forms the data base for most diagnostic investigations. Many biochemical reference ranges tend to have specificity for an organ and/or a limited range of pathological processes.  Interpretation of diagnostic biochemical profile provides all the data necessary for a broad investigation of a specific internal disease.    Profiles with limited data are best used for monitoring an established diagnosis; after a diagnosis using a complete blood panel have been already obtained.  The results of laboratory tests can be influenced by drugs your cat is already receiving and some can be influenced by a recent meal.  Fasting blood work is the most effective when looking for an underlying cause to your cats symptoms.

The function of blood is to transport oxygen and nutrients to the cells.  It also transports carbon dioxide and waste to the organs that are responsible for their breakdown and removal from the body. Additionally, blood is responsible for defending the body against viruses, bacteria and any other organisms that may enter the body.

Red blood cells, (RBC), are formed in the bone marrow.  The bone marrow produces new RBC’s constantly because the life span of a RBC is about 100 to120 days, depending on the animal.  These tiny workhorses carry oxygen to the body’s tissue.  Oxygen that is taken into the body attaches to the hemoglobin as the RBC’s pass through the lungs.  The RBC’s then deliver the oxygen to all the other cells in the body and take the carbon dioxide back to the lungs.

The body measures the number of RBC’s by evaluating the quantity of oxygen being supplied to its tissues. The number of RBC’s can be decreased if they are not produced in adequate numbers by the bone marrow, if their life span is shortened, (a condition called hemolysis), or if they are lost due to bleeding.  Increased red blood cell numbers is called polycythemia and is usually due to concentration of the blood due to dehydration.  Old red blood cells are removed from the blood stream by the spleen and the liver.

The number of RBC’s can be determined in several ways.  The quickest and easiest is called the hematocrit which also can be referred to as the packed cell volume, (PCV). To perform this test, a small amount of blood is placed in a glass tube and spun in a centrifuge.  The blood cells pack to the bottom of the tube and the fluid floats to the top. The PVC is the percent of blood, the actual cells, compared to the total volume of blood.  In normal cats, 40 to 50% of the blood is made up of blood cells and the remainder is plasma, or the clear liquid portion of the blood.  If the PCV is low, there are fewer red cells in the body than we would expect, (normal for a cat is 29-50).  This condition is referred to as anemia.  In severe cases of anemia, the cat would probably have pale pink to white membranes in its mouth and seem lethargic due to the fact that the cat is getting less oxygen than needed.  Anemia’s are further classified as regenerative or non regenerative.  In regenerative anemia, the body responds by releasing new immature red blood cells, called reticulocytes, into the circulation.  In nonregenerative anemia there are no or very few immature RBC’s in the blood sample and the body continues to lose RBC’s, but no new ones are produced.  A nonregenerative anemia is very, very serious and will become life-threatening in a very short period of time.

When the PVC is greater than 55, it is said to be elevated.  This is observed in dehydrated cats as their blood is becoming more concentrated.  In conditions such as some cases of shock, response to high altitudes, and diseases of the lungs, higher PVC will be noted.  Any condition that decreases the oxygen reaching the tissues of the body will cause higher numbers of red blood cells to be found in the CBC.

The actual numbers of RBC’s in a given quantity of blood is called the red count.  This is more difficult test than a hematocrit, due to the fact that the cell count is not measured as a percentage of anything, but rather the actual number of cells found in a microliter.  This is also a way of measuring the RBC’s in a blood sample.  The average red blood cell count for a cat is 6.1-11.9.

The final way to evaluate the RBC’s is by quantifying the amount of hemoglobin present.  In some anemia’s the actual number of RBC’s may not be very low, however if the cells contain less than the normal amount of hemoglobin, the signs of anemia could be quite severe.  The normal hemoglobin count for a cat is 9-15.6g/dl.

The other major type of blood cell is the white blood cells, (WBC).  They are also referred to as leukocytes.  There are more RBC’s than there are WBC’s.  In every sample there will normally be 600 to 700 RBC’s to every leukocyte present.  The major role of the white blood cells is to defend the body against invading organisms such as bacteria, viruses, and fungi.  There are different types of leukocytes, i.e. neutrophils, lymphocytes, monocytes, eosinophilos and basophils. The WBC is a total of the various kinds of white blood cells.

The number of WBC’s is usually elevated when the cats’ body is fighting a severe infection or stressed by metabolic toxins.  When a cat is extremely excited or frightened white blood cells will be released into the blood stream and the levels will rise.  The WBC count will be lower than normal if a particular cat has been weakened from a prolonged, debilitating disease and in some viral infections.

WBC’s are divided into two groups depending on how they react to the stains that are used to better observe them under a microscope.  There are granulocytes and agranulocytes.  The granulocytes absorb stain and the agranulocytes do not absorb stain used for microscopic observation.  The granulocytes include neutrophils, eosinophils, and the basophils.  Agranulocytes are the lymphocytes and monocytes.     

Neutrophils are formed in the bone marrow.  They have the ability to eat up or engulf foreign particles into their cells.  When the total numbers of neutropjils increase it is usually a sign of a bacterial infection or some form of extreme stress. In most viral infections the total number of neutrophils decreases.

Eosinophils are usually seen in fewer numbers that neutrophils.  They are also produced in the bone marrow.  Similarly, the esoinophils devour foreign particles into their cells.  The quantity of eosinophils increase in the circulating blood when the animals are suffering from an infection with parasites or have allergies.  Like neutrophils, eosinophils seen in extreme or prolonged stress decreases in numbers.

Basophils are the last of the granulocytes.  They are the least common of the WBC’s and in many samples, none are present.  Their function is unknown.  They are produced in the bone marrow.

Lymphocytes help fight infection and produce antibodies against infectious agents such as viruses, bacteria etc. Lymphocytes are produced in lymph nodes throughout the body.  In kittens under stress, lymphocytes may be lost in some types of diarrhea.  Certain drugs such as prednisone will decrease the number of lymphocytes in the blood stream.     

Monocytes may be increased in cats with chronic infections.

Platelets are produced in the bone marrow and are involved in the process of making a blood clot.  Platelets live a few weeks and are constantly being replaced.  Low platelet counts occur if the bone marrow is damaged and doesn’t produce them or if the platelets are destroyed at a faster rate than normal.    The two primary causes of platelet destruction are immune-mediated destruction and disseminated intravascular coagulation.  Immune-mediated thrombocytopenia happens when the cat’s immune system destroys platelets. Disseminated intravascular coagulation is a complex problem in which blood clots form in the body using the platelets faster than the bone marrow can produce new ones.  Animals with a low platelet count can bruise easily and often have blood in their urine or stools.

Some of the more commonly performed chemical testing are listed below:

Alanine aminotransferase (ALT)  is an enzyme produced in the liver cells.  Damage to these cells, such as in liver disease, leads to the enzyme being released into the blood stream where it is detected by its increase.  It is an indicator of liver problems whether primary, (infection, cancer etc.), or secondary, (circulation disturbance to the liver). The ALT test is considered to be liver specific in small animals.

Albumin (ALB) is the most abundant plasma protein and is formed in the liver.  Albumin acts like a sponge to hold water in the blood vessels.  When the albumin is decreased the pressure created by the heart forcing blood through the blood vessels cause fluid to leak out of the vessels and accumulates in body cavities such as the abdominal cavity or in tissues as edema.  Albumin is decreased if the liver is damaged and cannot produce an adequate amount of albumin or if albumin is lost through damaged intestine or in the urine due to kidney disease.  Low levels of albumin in the blood indicate the possibility of liver disease.  The only cause of increased albumin is dehydration. 

Alkaline phosphatase (ALP) originates from many tissues in the body.  When alkaline phosphatase is increased in the bloodstream of a cat the most common causes are liver and bone disease.  An elevated ALP can also be associated with hyperthyroidism in cats.

Amylase is secreted by the pancreas and is important is normal digestion of starch.  High levels of Amylase in the blood indicate pancreatic inflammation or cancer, kidney disease, prostatic inflammation, diabetic ketoacidosis and liver cancer. Elevated levels of amylase can occur with obstruction of the bowel and other severe bowel diseases. Low levels can indicate malnutrition or starvation.

Bilirubin is produced by the liver from old red blood cells. Bilirubin is increased in the blood of cats with some types of liver disease, gallbladder disease or in cats that are destroying the red blood cells at a faster than normal rate, (hemolysis).  Large amounts of bilirubin in the bloodstream gives a yellow cast to the areas of the animal that are not covered with fur such as the tissues around the eye, gums and inside of the ears.  This is also called jaundice or icterus.

Total serum bilirubin values >10mmol/L in cats may be caused by a variety of conditions, such as anorexia, liver disease, renal disease, gastrointestinal disease, FIP etc.  Values above 50 mmol/L are generally caused by liver disease if the haematocrit is normal.  Bilirubinuria in cats is considered to be abnormal.  Hepatic lipidosis, cholangiohepatitis and FIP are common causes of feline hepatic disease.  Liver biopsy is essential for a definitive diagnosis and for determining long term prognosis.

BUN (Blood Urea Nitrogen) Blood urea nitrogen is a waste product that is produced by the liver from proteins from the diet.  It is eliminated from the cat’s body by the kidneys.  High levels indicate kidney failure or disease, dehydration, shock, high protein diet, certain toxin ingestions, poor circulation to the kidneys and urinary obstruction.  Low levels indicate liver disease or starvation.  Low levels of blood urea nitrogen can be seen in some genetic conditions.

Calcium is a mineral in the bloodstream that originates from the bones. It is utilized in bone and structural organization, enzyme function, blood coagulation in osmotic pressure and maintenance of fluid balances and is essential in muscle activity.  Calcium interrelates with any other system and has a close relationship to many enzymes and values measured in a blood profile. High levels of calcium indicate a dietary imbalance, kidney disease, excess intake of vitamin D and severe tissue trauma.  Low levels indicate dietary imbalance, diabetes, eclampsia, certain cancers, overdose of insulin and an overactive parathyroid gland.  Low blood calcium, (eclampsia), can occur in cats just before birthing or while they are nursing kittens.  Eclampsia causes the cat to have rigid muscles which is called teetany.  Animals poisoned with antifreeze may have very low blood calcium.

Chloride is an electrolyte.  Its role is to help the body maintain a normal acid balance in the blood.  High levels of chloride indicate dehydration, kidney disease, acidosis, (low blood pH).  Low levels indicate vomiting, diarrhea and metabolic alkalosis, (loss of acid from the body).

Cholesterol is important in the synthesis of certain hormones.  High levels are not as important as it is in people.  High cholesterol levels are implicated in vascular disease, and are of diagnostic importance in hypothyroidism.  It does not in itself diagnose any single disorder.  Low levels indicate liver disease, starvation, kidney disease, pancreatitis and diabetes.

Creatinine is a waste product that originates from muscles and is eliminated from the body by the kidneys.  An elevation of creatinine is due to kidney disease, dehydration, shock, certain toxin ingestions, poor circulation to the kidneys and urinary obstruction.  Both the creatinine and BUN increase in the bloodstream at the same time in cats with kidney disease.

Creatinine kinase (CK) is important in the storing of energy needed for muscle contractions.  Creatine kinase is useful in diagnosing skeletal muscle or cardiac muscle degeneration.  High levels indicate muscle trauma or damage such as due to seizures, surgery, bruises, inflammation, nutritional and degenerative diseases. Low levels are not clinically relevant.

Glucose is blood sugar that is a primary source of energy for the body.  High levels indicate stress, Cushing’s disease, diabetes, pancreatitis or can be due to certain medications.  Low levels can be caused by liver disease, pancreatic tumor, insulin overdose, missed meals and a severe bacterial infection.  Low blood sugar can be the cause of depression or seizures.

Magnesium (Mg) is an essential blood salt necessary for nerve function, activity of many enzymes, blood clotting, forming adenosine triphosphate, (ATP) and production of insulin.  Low levels can indicate poor kidney function diabetes & diarrhea.

Phosphorous is an abundant mineral in the body.  Calcium and phosphate work together to build and repair bones and teeth.  Phosphorus is used in the structural proteins of cell walls and in active metabolic enzymes and pathways. About 85% of phosphate is found in the bones, with the remaining 15% stored in the cells where it is responsible for energy metabolism as well as being an integral structural component of RNA and DNA.  Excess phosphate is filtered by the kidneys and excreted in the cat’s urine.  If the kidneys begin to fail, they are less able to rid the body of excess phosphate and the levels begin to build up.  Other causes of high phosphate include dietary imbalance, excess ingestion of vitamin D and severe tissue trauma.  Additionally, high phosphorus levels should be correlated with renal evaluations due to the fact that the renal system is closely involved in the control of phosphorus levels and thus urea and creatine are important adjunct determinations.  Low levels indicate dietary imbalance, certain cancers, overdose of insulin, diabetes, eclampsia and an overactive parathyroid gland.

Potassium is an essential electrolyte which performs several functions in the body.  It works with sodium and is very important in maintaining normal function of muscle and nerves.  It also maintains heart function, blood pressure and the body’s electrolyte balance and acid/alkali levels in cells and tissues.  High levels indicate diabetes, certain toxin ingestions, urinary obstruction, acute kidney failure and severe muscle damage.  Low levels, (hypokalemia), may be caused by vomiting & diarrhea, and dietary insufficiency.

Sodium works in combination with potassium and is very important in maintaining normal function of the muscle and nerves.  It is also an important electrolyte in every part of the cat’s body.  Sodium may increased in the cat’s body if the cat is dehydrated, has diabetes insipidus or excess intake of salt.  Low levels indicate starvation, severe diarrhea, vomiting and metabolic acidosis.

Total Protein (TP) includes albumin and larger proteins called globulins.  Globulins are a protein; a building block of cells and tissue. Globulins are components of the immune system used to fight diseases.  Since globulin contains antibodies, an increase in the cat’s globulin levels may indicate a parasite or a viral or bacterial infection. The cat’s diet and thyroid may need to be evaluated in cats with decreased globulin levels.

Proteins are the basic element of enzymes and antibodies, as well as many hormones and clotting agents.  Together with the other chief protein, Albumin, globulin has several functions in assisting the cat’s red blood cells, including the transportation of hormones and vitamins, regulating the acid to alkaline ratio, and providing the muscles and tissues with water and energy. 

If globulin numbers are of a concern, a test called a electrophoresis, can further break down globulin levels.  A problem might then be limited to the alpha, beta, or gamma globulin.  This will assist in narrowing down the problem levels.  An example such as inflammation can be severe when alpha globulin is increased, but more mild when the increase is in beta globulin.  An inflammatory condition known as Feline Infectious Peritonitis, (FIP), causes an increase in beta globulin.

Cats with high protein numbers might be suffering from dehydration, lymphoma, or infections such as tuberculosis and pneumonia.  Low protein numbers could indicate malnutrition, anemia, kidney or liver disease, hemorrhage, or gastrointestional disease.  It is important to note that cats on a high protein diet, such as a raw meat diet will normally show slightly higher protein numbers. 

Protein numbers can fluctuate with diet and metabolism.  Blood work showing a small rise in protein levels could be explained by a lack of water intake that day.  True medical issues are more correctly identified when protein levels are compared with symptoms the cat is presenting in addition to the other level of blood values.

Urea is formed in the liver and is mainly excreted by the kidneys.  Urea is useful in evaluating kidney function in conjunction with creatinine.  The majority of blood urea is synthesized in the liver from ammonia.  Once formed, urea diffuses freely throughout all body fluids.  The kidney is the most important route of urea excretion and as a result, urea is used as a barometer of renal function. 

An increase in urea may fall into one of three categories:

Prerenal-Fever, infection tissue necrosis and administration of corticosteroids and circulatory changes may result in an elevation of urea, as will increased protein digestion from intestinal bleeding will cause an increase.

Renal-Increased urea values are seen when approximately 75% of the kidney filtering functions (nephrons), become non-functional.  Detection of renal disease cannot be made before 60-75% of nephrons are not functional.

Post-renal-An obstruction of the urinary tract increase urea values considerably.  The magnitude of the increase depends on the degree of the obstruction.  Urinalysis, especially urine specific gravity, is useful in determining whether elevated urea is pre-renal, renal or post-renal.

Blood and urine tests are performed to get an initial overview of the cat’s health and how the functions of the body organs are doing.  Some of the blood tests are very specific for a single organ, whereas other tests are affected by several organs.  The biochemical profile varies from laboratory to laboratory in which it was performed.  One must always know the normal ranges of a specific test to analyze the test results. 

When the results of the blood work are available to us, we are more efficiently equipped to determine the overall health of the cat.  The CBC indicates if an infection is present and to differentiate if it is a viral, bacterial or parasitic infection.  Additionally, a CBC can assist in the diagnosis or confirm disorders such as autoimmune diseases, anemia, allergies, leukemia and many other conditions.

Works Cited

    "Biochemical Proflies and Individual Biochemical Parameters." Veterinary Diagnostic Laboratory UK, Axiom Veterinary Laboratories, The Quality Clinical Pathology Service. 21 Mar. 2011 <http://www.axiomvetlab.com/>.

    "Biochemical Profile in Cats." Biochemical Profile in Cats - Cat World. 21 Mar. 2011 <http://www.cat-world.comau/biochemical-profile-in-cats>.

    Foster, DVM, Race. "Blood Cells & Complete Blood Counts (CBC) in Animals." Dr. Foster & Smith, Inc. PetEducation.com. 13 Mar. 2011 <http://www.peteducation.com/article_print.cfm?C=O+1302+1473&edu=987>.

    Peterson, Leigh A. "Globulin Levels in Cats." EHow.com. 12 Mar. 2011 <http:www.ehow.com/_5387491_globulin-levels-cats.html>.

    Ruben, Dawn. "Understanding Blood Work: The Biochemical Profile for Cats." Cats Only Veterinary Hospital. 13 Mar. 2011 <http://www.catsonnlyveterinaryhospital.vetsuite.com/Templates/ContentPages/Articles/ViewArticlesContent.aspx?Id=748>.

    "What Do Those Lab Tests Mean?" Washington State University. College of Veterinary Medicine. 13 Mar. 2011 <http://www.vetmed.wsu.edu/cliented/lab.aspx>.