Evaluating the Results and Their Potential Meaning

These are only a few of the many components evaluated in a complete blood count:

Bone Marrow Replaces Red Blood Cells

Red blood cells constitute approximately 30 to 40 percent of the blood volume and carry oxygen from the lungs to tissues via iron-based molecules called hemoglobin. Feline red blood cells normally circulate for about 70 days before they are removed from the blood stream and the bone marrow replaces them.

Too few red blood cells in the circulation is called anemia, which may result from blood loss or lack of sufficient production. Excess numbers may mean overproduction of red blood cells, dehydration or a lung disorder.

However, cats often experience contraction of the spleen, which stores red blood cells, when they’re stressed at the clinic. This fear causes a release of adrenaline, which causes the spleen to contract, releasing excess red blood cells, sometimes resulting in an abnormally high result.

Measurements of various red blood components:

HCT: Hematocrit, also known as Packed Cell Volume or PCV. This is the percentage of blood volume occupied by the red blood cells present.

HGB: Hemoglobin concentration of the blood. This measurement is related to oxygen-carrying capacity of the blood and can help determine the cause and severity in anemia.

MCV: Mean Corpuscular Volume, also Mean Cell Volume, a measurement of the average volume of red blood cells. MCV may be elevated in liver disease or vitamin B12 deficiency. Kidney disease can cause low a reading.

RDW: Red Cell Distribution Width. If a cat is anemic, this test can help differentiate between anemia from single or multiple causes. Results may be abnormal in liver disease.

MCH: Mean Corpuscular/Cell Hemoglobin, an estimate of the amount of hemoglobin in red blood cells.

MCHC: Mean Corpuscular/Cell Hemoglobin Concentration, the concentration of hemoglobin present in red blood cells. When these two counts are high, red blood cells may not be produced normally, or they may indicate low levels of B12 or folic acid.

White Blood Cells: The Disease Fighters

White blood cells (leukocytes), which are a part of the immune system, defend your cat against disease by detecting, attacking and removing foreign organisms such as bacteria or viruses, irritants, and dead tissue. There are multiple types of white cells, each with its own sub-types, functions and means by which they are measured.

Leukocyte differential: This lists the percentages of different white blood cells.

Neutrophils: These destroy infectious organisms, increasing in bacterial infections and decreasing with some viral infections or exposure to toxins. Birmans may have abnormal neutrophil results as well as possible different readings for other white blood counts.

Lymphocytes: These are divided into B- and T-cells. B-cells produce antibodies that attack foreign material and disease-inducing organisms, while T-cells cause other cells to destroy viruses and foreign matter. Lower counts are seen in the beginning of many types of infection and higher counts may be seen with autoimmune disease. Lymphoma usually also causes elevations of certain types of lymphocytes.

Monocytes: These cells consume foreign substances and infectious organisms, and aid in repair of injured or inflamed tissue. Monocyte numbers may be increased with leukemia, traumatic injury and fungal infection.

Eosinophils: These cells increase in parasitic infestations, allergic responses, dermatitis and inflammatory bowel disease. Decreased numbers may occur under stressful conditions.

Basophils: These cells usually have the lowest counts of all white blood cells. They work with eosinophils during an allergic response, primarily in skin or mucous membranes. A cat frightened at the clinic can have elevated lymphocytes and neutrophils.

Platelets Form a Clot That Slows Bleeding

Platelets come together to form the initial clot following injury to blood vessels, triggering a number of chemical reactions that recruit other platelets and factors to the site of injury. This ultimately results in the formation of a larger clot that slows/stops bleeding.

PLT, PCT: Platelet and Platelet Crit measures the number of clotting platelets present and their percentage of total volume in a blood sample. Increases may be found in inflammatory bowel disease, lung or gastrointestinal cancers and anemias. Decreased volume may indicate blood cancer, liver disease and autoimmune conditions or infections, including feline leukemia virus or feline immunodeficiency virus.

MPV: Mean Platelet Volume measures the average size of platelets.

PDW: Platelet Distribution Width measures the uniformity of platelet size. This helps diagnose the reason platelet production may be too high or low. A cat may need additional tests to rule out or diagnose infection, autoimmune conditions, liver disease, bleeding disorders, and iron, B12 or folate deficiencies, and the risk of life-threatening bleeding.