http://www.dolittler.com/2009/05/02/Blo ... e-CBC.html
“You want $99 to test his blood before his dentistry? Seriously? I’m thinking maybe we’ll skip the whole dental thing. The anesthesia freaks me out, anyway.”
That’s not usually how it goes where I work. Clients tend to be more polite, at least. But dentistry is one of those wellness services that suffers in a slumping economy. At our place, it’s clear that, despite their respectful receptiveness, fewer clients are making it back for the actual procedure. About 25% less over this time last year.
Luckily, the expense of the necessary pre-anesthetic blood work is NOT standing in the way of my clients’ dentals. That service is still holding strong––likely because we bundle it with basic annual visits so that nearly every pet gets their blood tested annually. But hospitals who don’t take this step are seeing an even bigger slump in their dental care and other wellness services that require blood work.
And I think I know why: Because pet owners need to be educated to understand the value of what they’re buying. Adding in comprehensive blood work with the annual physical and fecal test (with or without vaccines) adds REAL value to a pet’s healthcare regimen. Nonetheless, its PERCEIVED value is negligible unless an owner is informed of how incredibly useful this information can be.
In other words, pet owners like you will NOT buy blood work (and, most importantly, your pets won't get it) if you have no idea what it’s all about. Here’s a short list of common misperceptions I encounter on this front:
1-Some pet owners assume that blood work for their pet means the heartworm test only.
They sometimes arrive at my hospital fresh from elsewhere informing me that we don’t need to draw their pet’s blood because it was just done a month or two earlier. The faxed-over records indicate a heartworm test every year...but nothing more.
2-Blood work is all the same, everywhere.
A corollary to #1, this common misconception assumes that comprehensive blood work is the same the world around. In Miami, for example, complete blood work may be different from that in Minnesota, Montreal, London, Tel Aviv or California. (e.g., Here in South Florida, we tend to include heartworm and tick disease tests for dogs; feline leukemia, FIV and heartworm antibody tests for cats.)
3-Evaluating blood work is a procedure that’s acceptably performed every few years.
Consider that your pet’s lifespan is much shorter than ours. Pets approaching their geriatric years are best served by semi-annual blood work. Pets without major concerns shouldn’t go more than a year without it. Any animal undergoing an anesthetic procedure should ideally have current (within a month) blood work. And sick pets may need it monthly, weekly, daily or hourly, depending on their condition and its severity.
Beyond the common misperceptions lingers the question of what this all means and why it’s considered so critical. Here’s an explanation:
The most commonly accepted comprehensive “blood work” for pre-anesthetic evaluation includes a minimum of two tests, the “CBC” (stands for “complete blood count”) and “chemistry” (or “chemical panel”). Think of it as one test for the cells in the blood (CBC) and another for the components of the fluid part of the blood (chemistry).
The CBC (blood cell analysis)...
1) looks at the red blood cells, counts them and takes some measures about how they’re shaped.
It checks the total number of red blood cells and the hemoglobin level (the oxygen carrying molecule in the blood, which is found inside the red blood cells). The red blood cell count and hemoglobin levels tell us whether your pet might be anemic (low red blood cell count, low hemoglobin level) or polycythemic (too many red blood cells, which may indicate dehydration and other disorders) and tells us quite a bit about the health of these cells and what might be happening in your pet’s bone marrow, spleen or kidneys.
You might also want to know what the "hematocrit" is (also called the PCV or “packed cell volume”). This very commonly mentioned part of the CBC is a measure of the percentage of red blood cells in the total volume of blood. A high hematocrit percentage (over 45%) can indicate dehydration or an absolute excess of red blood cells (polycythemia). A low count usually assists in your diagnosis of anemia.
2) It also counts the total amount of and different kinds of white blood cells.
This paints a picture that explains which kind of white cells are in greatest abundance, along with their total numbers. This is crucial for an investigation of your pet’s infection or inflammation status. We wouldn’t want to do surgery––unless we HAD to––if these cells were elevated or significantly out of whack.
Neutrophils are the most abundant white blood cell type. When these are elevated we tend to worry about bacterial infections. With viruses, the total white blood cell count is commonly depleted. But these are simplifications. Try not to take them as absolutes.
3) Finally, it tells us about your pet’s platelets.
These tiny bits of clotting proteins are crucial. Low platelet levels can be scary when it comes time to stop bleeding. You wouldn’t want your pet to undergo surgery if these were low. Not only could she bleed to death, the low levels of platelets could indicate life-threatening diseases or serious infections (such as those spread by ticks).
4) The CBC may help identify, confirm or support common diseases or disorders.
Here's a brief list of these:
autoimmune diseases (like autoimmune hemolytic anemia)
blood cancers (certain lymphomas, for example)
kidney disease (as with chronic renal failure)
tick-borne diseases (like Ehrlichia or Lyme)
viral infections (like Parvo or Panleukopenia)
bone marrow diseases
parasitic diseases (like hemobartonella in cats)
poisoning (Tylenol or onion toxicity, for example)
Here's a cool pic outlining these above components:
http://www.dolittler.com/2009/05/03/Blo ... istry.html
Turns out this topic is gathering some steam here on Dolittler––as it is in veterinary minds across the spectrum of companion animal medicine. That’s why this topic requires a two-post treatment to properly address.
Though blood work is an increasingly common component of every pet’s medical care, not every veterinarian will draw your pet’s blood automatically. That’s why you need to understand why we do so and what we hope to learn by gathering this kind of [sometimes expensive] evidence.
For your better understanding, here are the typical reasons we’ll go so far as to poke your pet and recover their “red gold”:
Because he’s sick and we’re unsure why or need more information about how his body is responding to a certain disease or process.
Because her disease is worsening or improving in ways we need to measure so that we can adjust our treatments (medications, etc.).
Because we’re considering a treatment regimen for your pet that requires long-term medications that can do damage to pets with certain risk factors (such as pain relievers for osteoarthritis in pets with pre-existing liver or kidney disease).
Because your pet needs an anesthetic procedure and we want her to be as safe as possible throughout this process. Some diseases or disorders require that we change our protocols or defer anesthesia should they be present.
Because we like to keep an annual record of your pet’s basic bodily functions and blood work is one way to objectively measure these. Keeping track of how these change is often crucial to how we optimize your pet’s care.
That said, let me first reiterate: The most common kinds of blood work are aimed at comprehensively testing the body’s functions and searching for signs of disease and disorder. They include the CBC (see yesterday’s post) and blood chemistry (AKA, “chemistry” or “chem”).
If the CBC (complete blood count) tests the blood cells themselves, the blood chemistry is all about testing the fluid the blood cells utilize to course through a pet’s body. This fluid’s components reflect the chemical elements utilized, filtered or produced by certain organs, thereby offering up information on their basic health and potential “dis-ease.”
Makes sense, right?
More specifically, here are the “chemicals” we like to measure most commonly and why:
These elements indicate, in a general way, how well a pet’s liver is functioning.
alkaline phosphatase (“alk phos,” SAP or ALP)
Liver injury, drugs, bone injury, skeletal diseases, cancer, pregnancy and normal growth can all elevate this enzyme’s level. Gastrointestinal diseases and endocrine diseases (like Cushing’s) can also raise its levels. Too low? Protein and vitamin deficiency (and severe, end-stage liver disease) can deplete it.
alanine transaminase (alanine aminotransferase, ALT)
Toxins, drugs, liver damage and kidney infections can all raise it. Decreased bile flow can drop it (as when a liver is “congested”). Mild elevations don’t stress us (in the absence of symptoms), but follow-up blood work is always necessary in these cases.
bilirubin total (T Bili)
Toxicity (poisoning), some forms of anemia and liver disease can all raise this measure of bile pigment (produced by the liver). Certain kinds of malnutrition, too-fatty diets and an end-stage, diseased liver may be accompanied by its low levels.
This protein is produced by the liver. As such, its depletion tells us something might be up with this organ. But malnutrition can do it, too. Fever, infection, burns, swelling and low calcium levels are also likely to drop albumin levels. While rarely elevated, severe dehydration may sometimes raise it a bit.
When we say we’re testing your pet’s kidney function with blood work, these are the most common tests we look at.
blood urea nitrogen (BUN)
Kidney damage is what we think of first when the BUN (usually pronounced “B.U.N.”, not “bun”) is up. But certain drugs, intestinal bleeding, excessive protein intake, dehydration and extreme exercise can raise it. When it’s low, we tend to think poor nutrition, poor gastrointestinal absorption or even liver damage in some cases.
Because the kidneys are supposed to filter out this chemical, its elevation always points us in the direction of kidney damage or dehydration. Muscle breakdown (as with extreme exercise) can also flood the body with creatinine while certain drugs can impair the kidney’s filtration of it. Confusingly, low levels may indicate kidney damage, protein starvation, liver disease, or pregnancy.
creatine kinase (CK, CPK)
This enzyme usually indicates either kidney trouble, dehydration or muscle breakdown, as with extreme stress, injury or exercise.
These individual elements are measured to determine the interaction of a myriad of complex processes. They may go along with certain illnesses or disorders and knowing their true value helps us guide our treatment options, especially when it comes to fluid therapy.
The pancreas is a sensitive gastrointestinal and endocrine (hormone-producing) organ that’s easily insulted. Pets with high levels of the following two enzymes may be experiencing acute (sudden-onset) or chronic (long-standing) pancreatitis.
Got diabetes? Stressed? Depleted your blood sugar with seizures? Has your tiny-breed puppy suddenly collapsed? Has she perhaps eaten some poisons (like Xylitol)? Glucose is the go-to test for so many troubles it’s impossible to list them all here. In any case, this “blood sugar” molecule, whether too high or too low, is a common indicator of mild and serious problems, alike.
Vomiting, diarrhea, liver disease, poor nutritional gastrointestinal malabsorption, dehydration will all raise it. Lupus, liver disease, chronic infections and leukemia will all drop it.
That’s my summary. But don’t be fooled: the complex interaction of components in the blood, coupled with other processes as they invariably are, may make interpreting these findings not-so straightforward (and that's an understatement). When one goes up, another may come down––and vice-versa.
That’s why an understanding of these test results is a necessarily “holistic” process in which we take our individual patients’ findings (on physical, CBC, other lab tests, X-rays and/or more sophisticated imaging) and put them all together. Even then, it’s nowhere like it is on Star Trek.
Sigh...if I only had a Tricorder...