The white blood cell count (WBC) is a valuable diagnostic tool. Along with other tests, medical history and symptoms, it reveals a lot about the state of a cat's health. If Muffin's older or feeling punky, chances are her vet will use this indicator to help gauge her health.
WBC: Part of the CBC
The complete blood test, commonly known as the CBC, is used to help diagnose disease or pinpoint injury, as well as give a good overview of the state of Muffin's health. A cat doesn't have to be sick or old to have a CBC -- some vets include them as part of wellness exams so they can get a history of "normal" levels for a cat. The results can be compared over time to gauge how a cat's health is progressing. Chronically ill or senior cats may have blood tests conducted more frequently to monitor health. The CBC measures a variety of things, including white blood cell count (WBC), red blood cell count (RBC), platelets (PLT), hematocrit (HCT) and hemoglobin (Hgb). A chemistry profile is often conducted at the same time. The results of both tests are used to provide a good overview of Muffin's health.
When your vet conducts a CBC the cells are counted and viewed on a blood smear, which is helpful for viewing certain conditions such as parasites or cancer. White blood cells are measured as thousands per cubic milliliter (K/uL). The normal range in a cat is between 5.5 and 19.5, meaning under normal conditions Muffin should have between 5,500 and 19,500 white blood cells per cubic milliliter of blood. Low WBCs can indicate viral infections, bone marrow issues or poisoning; in these cases, the white blood cells are concentrated in the affected area and not circulating in the blood. Elevated WBCs occur when an area of the body is inflamed and the blood cells are responding in reaction; they can indicate infection, inflammation and some types of cancer.
There are five types of white blood cells: neutrophils, eosinophils, monocytes, lymphocytes and basophils, all known as the differential. The distribution of these cells can help focus on the cause of an illness. Neutrophils are the primary white blood cells that fight infection, so if Muffin's neutrophil level is high, she's likely got an infection. Since monocytes help in this battle, a high level of monocytes indicate the same condition. Lymphocytes also help fight infection as well as develop antibodies to ward off future attacks. High levels of these cells indicate infection, viral diseases and certain forms of cancer. Eosinophils are often elevated when a cat has parasites or an allergic reaction. Basophils aren't very common and tend to appear in cases of parasite infection, particularly in animals with heartworm.
One Piece of a Puzzle
Generally a high white blood cell count means that Muffin has an infection or virus. However, the WBC is just one piece of the diagnostic puzzle. The rest of the blood work, such as platelets and red blood cell count, must be considered. The vet will also have to account for Muffin's medical history, her symptoms and her lifestyle. If a chemistry panel was conducted, that will be included in the diagnostic process.