Lab work.

Red Blood Cell

This is going to be the first of a series on the lab results you get when we run blood work or a urinalysis at the clinic or when we send them out. I am going to break it down by system, sort of. Not every aspect of blood work is that straight forward, for example the things we point out to you and say they indicate liver disease, usually they don't. Sometimes they do but usually they are secondary to other issues or non-issues in the body. I am going to use the nomenclature used by the laboratory we use as well as our in house laboratory equipment. It might differ from your veterinarian's lab nomenclature but you should be able to decipher the differences.

We are going to start this series with the part of the blood work that looks at the blood cells; red cells, white cells and platelets. Specifically we will start with the red cell indices.

Red blood cells or erythrocytes are the oxygen transporters in the body. They also produce several different compounds that cause the blood vessels to dilate in response to stress or damage to the cells. In mammals these cells do not have a nucleus. All other vertebrates do have a nucleus within their red blood cells except for the Crocodile Ice fish who don't have any red blood cells or hemoglobin.

When we are measuring the red blood cells in veterinary medicine we are looking at several indices. Red blood cells are the cells lost in anemia, a condition that accompanies several disease processes. They also become increasingly concentrated in dehydration and a few rare conditions.

PCV/HCT: Packed Cell Volume. This is probably the one of the simplest and most important diagnostics that we can run in the veterinary facility with limited necessary equipment. It is the percentage of red cells and red material that centrifuges out of solution when the blood is spun at high speed in a closed container. We can typically do this in less than ten minutes and the cost is variable between hospitals but is typically very low. In lab results run on in house lab equipment or arrived at on lab results sent to a diagnostic lab will report back the PCV as the hematocrit or HCT.

RBC: this is the red blood cell count and is a calculated value representing the total number of red blood cells in a specific amount of blood. This value is of little significance by itself but it used to calculate some of the other values we are going to use to evaluate the overall health of the red blood cell population and the oxygen carrying capabilities of our patients.

HGB: Hemoglobin Concentration. This is the most accurate measurement we have of the oxygen carrying capability of the blood. It is approximately 1/3 of the PCV or HCT. Exact value are arrived at by destroying all of the red blood cells within a sample using college level chemistry. The HBG levels also allow for calculation of some of the values we use to qualify anemia.

MCV: Mean Cell Volume. This is a calculated estimate of the average size of a circulating red blood cell. This gives us an idea of how old, damaged and possible diseased the cells might be as they circulate and help to qualify how the organs and systems responsible for blood production are responding to disease or insult. It is arrived at by multiplying the PCV or HCT by 10 and then dividing by the RBC value.

MCH: Mean Cell Hemoglobin. This value isn't used frequently but still shows up on lab results. Maybe it's for the old timers and gunners. Those vets who are analogous to the guys at the gym still doing Russian get ups. This is arrived at by multiplying the HGB by 10 and dividing by the RBC. It has been replaced by the MCHC in most situations.

MCHC: Mean Cell Hemoglobin Content. The is an estimate of the concentration of hemoglobin in the average red blood cell. It is arrived at by multiplying the HGB by 10 and dividing by the PCV. This number is decreased in animals in whom the body is responding to anemia by rapidly producing red blood cells. As red blood cells are produced rapidly there is less time to "fill" them with hemoglobin. Elevated MCHC values are almost always due to hemolysis, typically a laboratory artifact although hemolysis can be seen with certain diseases. This is arrived at by multiplying the HGB by 10 and dividing that by the PCV.

NRBC: Nucleated Red Blood Cell. When the body is making red blood cells in a hurry it doesn't bother to wait until tey are mature and will "toss" them out into circulation while they still contain a nucleus. This is a good indication that the body is responding to a condition removing red blood cells from circulation. It is arrived at by looking for nucleated red blood cells. 

Red blood cell indices will change in response to several conditions some of which are not pathogenic. For example. living at higher altitudes will cause the body to increase the number of red blood cells in response to the lower oxygen content of the air. The RBC, PCV and HCT will also increase in response to dehydration. Vomiting and diarrhea are the most common causes of dehydration in the veterinary clinic and if the level of dehydration is affecting the red blood cell indices it is probably also affecting the electrolyte concentrations and blood viscosity and should be addressed.

The major condition we qualify and quantify with red blood cell indices is anemia. Anemia is present with many diseases and will be present with nearly any long standing inflammatory condition. Anemia is a decrease in the number of circulating red blood cells and as a result there is a loss in the oxygen carrying capacity of the blood. We first categorize anemia as either regenerative or non-regenerative based on the MCV, MCHC and NRBC. Regenerative anemia indicates that the body is trying to compensate and respond and may improve with just minor intervention. Non regenerative anemia typically is going to require further investigation and while some may improve with minor intervention a non regenerative anemia is typically indicative of serious disease processes within the body. If your veterinarian diagnoses your pet with anemia you will want to have that monitored closely until the cause can be identified and dealt with.

 

 

Comments

[Cat food]

Cats who are sick with other illness may become anemic quite easily. Anemia is the state of having a low count of erythrocytes, a type of red blood cell. Symptoms of feline anemia include a loss of color of the cat's mucous membranes, observed lethargy and a rapid pulse. Testing must be done to determine the cause of anemia before appropriate treatment can begin.