Dr. Suzanne Stack
There are two articles here. One is Reading Blood Work. The other details the differences in a greyhound’s blood work from other dogs.
Reading Blood Work
When that “basic profile” comes back from the lab, what can it tell you? The highlights in greyhounds are:
The CBC (complete blood count) tells how many of each kind of blood cell is circulating. RBCs (red blood cells) contribute to the HCT or PCV (hematocrit or packed cell volume = the concentration of red blood cells in the sample). Hgb is the amount of hemoglobin in the RBCs. These numbers are normally high in greyhounds, low in anemia. MCV, MCH, and MCHC are calculations derived from RBC, PCV, and Hgb.
The WBC (white blood cell) count is a total of the different kinds of WBCs in the sample – segmented neutrophils, bands, lymphocytes, monocytes, and eosinophils. The breakdown of WBCs is called the differential (diff) and by its makeup can indicate a normal dog or possible infection/inflammation. The “diff” gives the doctor clues to what process or disease might be causing an abnormal WBC. WBCs can normally run low in greyhounds.
Platelets are the last component of the CBC. Platelets are the blood cells that form a “platelet plug” to stop the bleeding when you cut your finger. Greyhounds can run under or on the low end of normal platelet counts.
The Chem Panel
The lab uses serum (what is left of whole blood once the cells are removed) to determine approximately 20 “blood chemistries.” There are many other tests that can be run on serum. Most “chem panels” include:
Total Protein = the sum total of Albumin + Globulin
– a protein made in the liver
– can be lost through damaged kidneys or intestines
– a protein produced in response to antigenic stimulation
– increased in chronic infections and some cancers
BUN – blood urea nitrogen
– increased in dehydration or kidney disease
– decreased in liver disease
Creatinine – also increased in kidney disease
– another measure of kidney function less affected by dehydration than BUN
– normally higher in greyhounds than other dogs
ALT (SGPT) – alanine transferase
– released from damaged liver cells
AST (SGOT) – aspartate transferase
– increased in liver damage, muscle damage (including intramuscular injections), or hemolysis (breakdown of RBCs). The hemolysis can be as simple as from a difficult blood draw.
ALKP (SAP) – serum alkaline phosphatase
– increased with liver disease, Cushings, steroids, some cancers & infections. Normally high in young, growing dogs.
T. Bili – total bilirubin
– pigment increased in liver disease or hemolysis which causes dog, serum, and/or urine to turn yellow (jaundice = icterus)
CPK – creatine phosphokinase
– enzyme released from damaged skeletal & heart muscle
– digestive enzyme increased in pancreatitis, intestinal disease, or kidney failure
– digestive enzyme which is more specific for pancreatitis
– rises after eating or from pancreatitis, diabetes, hypothyroidism, or glomerulonephritis.
– doesn’t clog arteries in dogs.
Glucose – “blood sugar”
– rises in diabetes, pancreatitis, seizures, or severe near-death type stress
– decreased in sepsis, insulinoma tumor, baby pups who don’t eat often enough, but most often from sample sitting around too long before centrifuging
– increased in lymphoma & other cancers
– decreased in kidney failure, post-whelping seizures, & hypoparathyroidism
– increased in kidney failure
The electrolytes TCO2, Cl-, K+, & Na+ show a wide variety of derangements in different diseases.
TCO2 – total carbon dioxide
Cl – chloride
K+ – potassium
Na+ – sodium
Lastly are 4 calculations:
A/G ratio – albumin/globulin ratio
– albumin should predominate over globulin in the normal dog
B/C ratio – BUN/creatinine ratio
– helps distinguish dehydration from true kidney failure
Na/K ratio – sodium/potassium ratio
– screens for Addison’s disease
Anion gap = (Na + K) – (Cl + bicarbonate)
– reflects acid/base status
There are many other less important or more obscure possibilities for elevations and decreases in these parameters that were omitted for space and clarity. Many values are only something to worry about if they’re either elevated or decreased, but not necessarily both. These are the basics.
Differences with Greyhound’s Blood Work
Greyhound blood work has enough differences from “other dog” blood work to sometimes make it deceivingly “normal” or “abnormal” if one isn’t familiar with these differences. The salient differences are discussed below.
CBC = Complete Blood Count
RBC = Red Blood Cells
Hgb = Hemoglobin
PCV / HCT = Packed Cell Volume / Hematocrit
WBC = White Blood Cells
NORMAL VALUES FOR:
Greyhounds Other Dogs
RBC: 7.4 – 9.0 5.5 – 8.5
Hgb: 19.0 – 21.5 12.0 – 18.0
PCV: 55 – 65 37 – 55
Greyhounds have significantly more red blood cells than other breeds. This elevates parameters for RBC, hemoglobin, and PCV / HCT, and is the reason greyhounds are so desirable as blood donors. Most veterinarians are aware of this difference. Never accept a diagnosis of polycythemia – a once-in-a-lifetime-rare diagnosis of pathologic red cell overproduction – in a greyhound.
Conversely, never interpret a greyhound PCV in the 30’s – low 40’s as being normal just because it is for other dogs. A greyhound with a PCV in the 30’s – low 40’s is an anemic greyhound. Here in Arizona, a greyhound PCV < 50 is a red flag to check for Ehrlichia.
Greyhound: 3.5 – 6.5 Other dog: 6.0 – 17.0
Other greyhound CBC changes are less well known. The greyhound’s normally low WBC has caused more than one healthy greyhound to undergo a bone marrow biopsy in search of “cancer” or some other cause of the “low WBC.”
Greyhound: 80,000 – 200,000 Other dog: 150,000 – 400,000
Likewise, greyhound platelet numbers are lower on average than other breeds, which might be mistakenly interpreted as a problem. It is thought that greyhound WBCs, platelets, and total protein may be lower to physiologically “make room” in the bloodstream for the increased red cell load.
Confounding these normally low WBC and platelet numbers is the fact that Ehrlichia, a common blood parasite of greyhounds, can lower WBC and platelet counts. So if there is any doubt as to whether the WBC / platelet counts are normal, an Ehrlichia titer is always in order. The other classic changes with Ehrlichia are lowered PCV and elevated globulin and total protein. But bear in mind that every greyhound will not have every change, and Ehrlichia greyhounds can have normal CBCs.
T.P. = Total Protein
NORMAL VALUES FOR:
Greyhound: 4.5 – 6.2 Greyhound: 2.1 – 3.2
Other dog: 5.4 – 7.8 Other dog: 2.8 – 4.2
Greyhound total proteins tend to run on the low end of normal – T.P.s in the 5.0’s and 6.0’s are the norm. While the albumin fraction of T.P. is the same as other dogs, the globulin component is lower.
Greyhounds: .8 – 1.6 Other dogs: .0 – 1.0
Greyhound creatinines run higher than other breeds as a function of their large lean muscle mass. A study at the Auburn University College of Veterinary Medicine found that 80% of retired greyhounds they sampled had creatinine values up to 1.6 times as high as the top of the standard reference range for “other dogs.” As a lone finding, an “elevated creatinine” is not indicative of impending kidney failure. If the BUN and urinalysis are normal, so is the “elevated” creatinine.
Greyhounds: .5 – 3.6 (mean 1.47+/- .63) Other dogs: 1.52 – 3.60
These figures are from a University of Florida study of thyroid function in 221 greyhounds – 97 racers, 99 broods, and 25 studs – so it included both racers and “retired.” While greyhound thyroid levels are a whole chapter unto themselves, a good rule of thumb is that greyhound T4s run about half that of other breeds.
And lastly, the good news – greyhound urinalysis is the same as other breeds. It is normal for males to have small to moderate amounts of bilirubin in the urine.