CBC

What does general bloodwork include?

General bloodwork usually includes a CBC (complete blood count) and chemistry profile, although may also include a thyroid hormone level (T4), particularly for older patients or those exhibiting symptoms consistent with hypo or hyperthyroidism.  Overall, bloodwork is an essential diagnostic tool for sick and healthy patients alike, as it provides important information about your pet’s general health and well-being.  In many instances it is used as a screening tool for illness or can help determine contraindications to putting an animal under general anesthesia or performing specific procedures.  Bloodwork is also performed often to monitor cell counts and internal organ function before, during, or after administration of various drugs, such as chemotherapy, non-steroidal anti-inflammatory medications, hyperthyroid drugs, antibiotics, anti-fungals, or anti-epileptic medications.   

How is bloodwork collected?

Bloodwork is collected by venipuncture (inserting a small needle attached to a syringe into a vein and aspirating back blood).  This procedure causes minimal to no discomfort, takes less than 5 minutes, and has limited to no side effects. 

What is a CBC?

A CBC (which stands for “complete blood count”) is used to evaluate the number and quality of blood cells in circulation, including red blood cells (cells that carry oxygen to body tissues and dispose of carbon dioxide), white blood cells (cells that fight infection and play a role in immune regulation), and platelets (cell fragments that help blood clot).  A CBC can tell the veterinarian a lot about the patient, such as whether or not there is evidence of anemia (a low red blood cell count), an infection (either high or low white blood cell count), inflammation (a high white blood cell count), blood-borne parasites, leukemia (cancer of blood cells that arises from the bone marrow), or other cancer cells in circulation (such as stage V lymphomas or mastocytosis).  As mentioned above, certain drugs can also alter cell counts or cause anemia (either directly or through gastrointestinal bleeding), so CBCs are often utilized to ensure that the patient is tolerating treatment with certain medications.    

How is a CBC useful for cancer patients?

Some patients with cancer will have actual cancer cells in the bloodstream; however, aside from patients with hematopoietic (blood-borne) tumors (such as lymphomas, leukemias, and systemic mastocytosis or histiocytosis), many cancer patients will surprisingly have a normal CBC.  Overall, it is important to know whether or not cell counts are abnormal, as this may indicate bone marrow involvement with certain cancers or immune mediated destruction of blood cells secondary to cancer.  Abnormalities on a CBC may prompt your veterinarian to recommend a bone marrow aspirate or biopsy (see below for a description of this procedure) to determine if cancer is arising from or affecting the bone marrow, which can change prognosis and/or the treatment protocol utilized in various situations. 

In addition, prior to administration of any chemotherapeutic agent, it is necessary to confirm that the patient has enough white/red blood cells and platelets to receive treatment.  CBCs are also used to monitor cell counts during and after chemotherapy or radiation.  Although a drop in blood cell counts secondary to chemotherapy is almost always brief and temporary, a course of antibiotics and/or future dose reductions may be prescribed.