The Basics on Blood Results
GLVH
When your veterinarian discusses blood results it might seem like a lot of information flung your way with no time for clarification; or perhaps you don’t know what questions to ask; or maybe you are embarrassed to ask for clarification!
This blog post is to help break down a basic blood panel and help interpret those parameters. Of course, practice and experience can make interpretation more accurate than what is being brought to the table here today, but this will hopefully allow you, as a dedicated pet owner, a better understanding of blood results overall. Keep in mind you can always ask for a copy of your pet’s blood results to review at your leisure.
The Complete Blood Count (or CBC):
A CBC looks into what the cells within blood are telling us. Specifically, it examines the red blood cells (RBCs), white blood cells (WBCs), of which there are a variety; and lastly how the platelets are doing. Along with direct counts of the specific cells, there are a variety of related parameters that are accounted for. These include the size of RBCs and platelets, how much hemoglobin is present with RBCs, whether there is regeneration of red blood cells in the case of anemia and what the total solids are within that blood sample.
- Red blood cell parameter interpretation
o Assessment of the total number of RBCs
o Hematocrit also allows for evaluation of levels of RBCs in the body, low numbers of HCT or RBCs are indicative of anemia
o High levels of RBCs or HCT may indicate dehydration or a true elevation in cells
o MCV or mean corpuscular volume is the size of the RBC
o MCHC and MCH are measurements of mean concentration of hemoglobin within the RBCs in a sample or individual cell
o RDW is red cell distribution width and indicates the variation or difference between the smallest and largest red blood cells and may help indicate if regeneration is present or not as more immature cells are larger in size
- White blood cell parameter interpretation
o There is an overall WBC count, and individual cell counts of the 5 types of WBCs
o These 5 cell types include: neutrophils (or segmented neutrophils), lymphocytes, monocytes, eosinophils and basophils
o Each WBC type is differentiated by appearance and has their own interpretation based on if they are normal, elevated or decreased
o Often elevations can indicate types of inflammation or infection, acute or chronic cases, or even just a stress response to being in the clinic and having blood drawn in a patient
o Significant elevations can indicate severe infections or possible neoplasia of a particular blood cell line (leukemia)
- Platelet parameter interpretation:
o Total count of platelets present, low platelets can be concerning and should always be assessed by a direct blood film on a slide under the microscope
o Platelets are often falsely decreased as they tend to clump up within a sample
o MPV is mean platelet volume which indicates the overall size of the platelets, some breeds genetically have higher MPVs
o Excessive inflammation can also increase the MPV as the bone marrow is actively producing excess platelets releasing “shift platelets” that are larger in size than normal mature ones
- Total solids
o This is a measurement of all the none-cell components within the blood, such as proteins
o An elevation in this number can also suggest dehydration as the solids within the blood become more concentrated under those circumstances, it is often interpreted along with hematocrit to confirm that suspicion
The Biochemistry:
This is the section of blood work that looks at components of organ function, electrolytes, protein levels, and blood characteristics such as if a sample is lipemic (high in fat) or has the sample hemolyzed (break down of the RBCs) that can cause changes in sample interpretation. Biochemistry panels can be small with only a few values or quite large depending on what parameters are specifically being looked at.
- Liver enzymes
o ALT and AST are indicators of liver function along with ALP and GGT that more specifically indicate bile flow through the bile ducts towards the gallbladder
o The liver also produces many substances such as glucose, urea, albumin and cholesterol, so decreases in any of these values might indicate liver disease
o Bilirubin may also be included (total, free or conjugated) and it helps assess how the liver is functioning as it breaks down old RBCs and conjugates it into a form that can be excreted in bile
- Kidney enzymes
o Urea, Creatinine and if added on, SDMA (symmetric dimethylarginine) all point towards kidney function
o As these values become elevated this indicates reduced kidney function that could be acute or chronic, elevation is often referred to as azotemia
o Often times your vet will recommend testing your pet’s urine to determine if the azotemia is truly a kidney issue, or if it is something pre-renal (such as liver dysfunction or muscle wasting) or post-renal such as a urinary obstruction
- Pancreas enzymes
o Previously lipase and amylase were often used to assess the pancreas, but over time these values have been pushed aside as not being as helpful as they once were believed to be
o Today a more specific Pancreatic Lipase test can be added on and elevations in it are quite predictive of a patient experiencing pancreatitis
- Muscles
o AST and CK are enzymes that are released from muscle if there is damage or muscle wasting
o As you can see AST can be released from both the liver and muscle, as well as RBCs, so interpretation needs to go along with other parameters
- Electrolytes
o Usually assessing sodium (Na), chloride (Cl), potassium (K), calcium (Ca), phosphorus (P) and magnesium (Mg)
o All these electrolytes are important for normal bodily function and elevations or decreases in any of them can be detrimental to a patient
o Cardiac function, muscle function, movement of nutrients, nerve function, and fluid balance are all affected by electrolyte levels
o Calcium levels strongly correlate with Albumin as it binds to it, so low Albumin will likely also see low Ca, or the reverse
- Proteins
o Here we are getting counts of total protein, as well as specifically Albumin and Globulin
o Low proteins can indicate loss by some means such as through the gut, kidneys or fluid accumulation within a body cavity
o Elevated globulins may indicate chronic antigenic stimulation where the body is making globulins as the immune system is stimulated
o Elevated albumin can indicate dehydration or a high protein diet
- Glucose
o Elevations in glucose indicate diabetes mellitus
o Mild elevations can occur when the pet is stressed, which causes glucose to release into the blood at time of vet visit or blood draw
o Low levels can mean the sample sat for a while and the cell metabolism used it up within the blood tube
- Acidosis/alkalosis
o Values such as the anion gap, carbon dioxide (CO2) and Na:K ratio can be used to determine if a patient is in acidosis or alkalosis if they are sick
As always, this seems like a lot of information, but breaking it down in this way will hopefully give you a resource to look at when going back over your dogs or cats blood results. Your vet should be happy to clarify any results with you and explain their interpretation of any abnormalities and why they may be significant or not.
Watch for the October blog post going over what a urinalysis is and how to read those results!
Dr. Hillary