VetInfo Digest March 2003
Normal Values
What is a normal value?
Blood Chemistry
Blood Cell Counts
Immunology
Therapeutic Drug
Monitoring
Urinalysis
Physiologic Normals
Function Testing
Hormone Testing
This Month's Note:
The single most important thing to remember about normal blood count and blood chemistry values is that they are established using animals judged to be normal based on physical examination and medical history. Blood is drawn from these dogs and all values that fall within 47.5% of the midpoint are considered to be within the normal range. This means that 5% of dogs who appeared to be completely normal had a blood count or blood chemistry value outside the normal range, or approximately 1 in 20 dogs.
A blood chemistry panel and blood cell count comprises more than 20 tests in most cases. Therefore, it is not unusual to have at least one value outside the normal range. It is extremely important to remember that blood test values are most important when they are coupled with clinical signs that indicate disease or when two or more values relating to the same organ system are elevated or lower than expected.
It is almost always reasonable to retest when a lab value is outside the normal range but there is no other supporting evidence for a problem in the organ system the blood value relates to. If the value continues to be outside the normal range on subsequent testing a decision has to be made about whether to pursue other types of diagnostic tests, such as ultrasound examination, X-rays or exploratory surgery. When making these types of decisions don't forget to pay attention to how the patient is doing as much as the test results!
Normal Values:
It is very important when publishing lists of "normal" veterinary values to make the following disclaimer:
All laboratory values listed are general ranges. When evaluating test results from a specific laboratory you must use the normal values reported for that particular laboratory when making evaluations of the significance of blood work.
Normal values from one lab to another vary significantly in some cases. Studies indicate that the test variations are real and that they do impact on the decision making when using laboratory values for diagnostic purposes. These values can vary really widely. Just as an example, one of our labs lists the normal range for ALT as 5-70 IU/L for dogs and another lists it as 10 -105. IU/L. A person expecting a normal upper limit of 70 on this test might be truly worried about a value of 105 looking at lab work from the other lab -- but if the blood was run at that lab, the 105 value has to be considered to be within the normal limits.
It is also important to note that normal physiologic reference ranges, such as heart rate, respiratory rate and blood pressure are often established using dogs and cats who are acclimated to the procedures and are not stressed during the examination to establish normal values. A cat who hates to ride in the car, is frightened of dogs and remembers the last visit to the vet's involved vaccinations is very likely to have a heart rate that is above normal limits. A dog coming into the office after barking at trucks all the way to the office in a car on a warm day is likely to have a rapid respiratory rate. When it is important to establish what a pet's resting heart rate, resting respiratory rate or blood pressure really is, it may be necessary to allow the pet plenty of time to settle down at the veterinary office prior to measuring these values. Alternatively, owners can learn to count these values at home and report them to their vet, to try to get an accurate assessment of their true values. This can also be very important for some laboratory tests. Cats are notoriously able to elevate their blood sugar levels in response to stress. Both dogs and cats can have a "stress" elevation in white blood cell count that must be accounted for when interpreting test results.
Sample handling and even patient handling can have major impacts on blood chemistry values. Red blood cells continue to use glucose in a blood tube and they will use all the glucose in the blood sample within a few hours, which sometimes leads to startlingly low blood glucose values on test results, for example. Urinalysis test results are so significantly impacted by handling and storage of urine that observing for crystal formation is almost worthless within four hours and other values are impacted, as well.
Age related normals are not widely publicized in veterinary medicine, but it is clear that there are major differences between puppies and adult dogs for several of the chemistry and blood count values. It is theorized that there are probably some major variations in other laboratory normals, especially hormonal levels, between young adult animals and older animals. Thyroid hormone levels in cats decline with age and it is likely that cortisol levels in dogs are lower in older age, as well. This can be important when looking for high levels of hormone suggestive of diseases such as hyperthyroidism. An older cat may actually be hyperthyroid while the blood level values fall within the published normal ranges, which are established using younger cats.
The most significant changes to normal blood count and blood chemistry values in puppies and kittens occur in the red blood cell numbers. Puppies have lower red blood cell counts, which can be confusing when there is reason to suspect anemia and is also confusing when looking at disorders, such as heart disease, which normally causes rises in red blood cell counts. A person unaware that puppies normally have lower red blood cell counts than adults might miss a rise in RBC count in a puppy. The serum alkaline phosphatase levels are usually much higher in puppies and kittens, as well.
I have included the "common" units used in the United States and a separate listing for SI (Systeme International) units, which are used in many other countries, where I could find conversion factors. The U.S. units are listed first and the SI units second in the chart (indicated by value, SI). In most cases if only one value is listed it is the same in both systems. In a few cases I couldn't find a normal value listed or a conversion formula to make a calculation of the Systeme International unit.
Blood Chemistry Values
Test Name
Units
Dog
Cat
Test Name
Units
Dog
Cat
albumin
g/dl
2.5-4.2
2.2-3.5
folate
ng/ml
4-13
albumin, SI
g/L
25-42
22-35
ionized calcium
mmol/L
1.12 to 1.40
1.20 to 1.32
ALT (alanine transferase)
IU/L
10-80
5-70
iron (serum)
ug/dl
80-120
70-215
alkaline phosphatase (SAP)
IU/L
10-110
10-110
iron, SI
umol/L
14-32
12-38.5
ammonia
1-150
1-150
lactate
mg/dl
5-20
4-19
amylase
IU/L
200 to
1450
100 to
1500
lactate, SI
mmol/L
0.6-2.9
0.5-2.7
aspartate amino-
tranferase (AST)
IU/L
5-105
5-100
lactate dehydrogenase
(LDH)
IU/L
20-500
20-500
bile acid (fasting)
umol/L
0-10
0-5
lipase
IU/L
25-750
10-450
bile acid, 2hr after eating
umol/L
<25
<20
magnesium
mg/dl
1.2-2.6
1.5-3.1
bilirubin, total
mg/dl
<0.8
<0.5
magnesium, SI
mmol/L
0.8-1.2
0.8-0.9
bilirubin, total, SI
umol/L
2-17
2-15
osmolality
mmol/kg
270-320
270-320
blood urea nitrogen
BUN
mg/dl
8-25
9-28
phosphorous
mg/dl
2.5-5.3
3.8-7.0
BUN, SI
umol/L
3.5-7.1
5.9-10.5
phosphorous, SI
mmol/L
0.8-1.6
0.6-2.2
calcium
mg/dl
8.3-11.8
8.0-11.2
potassium
mEq/L
3.6-5.5
3.8-5.5
calcium, SI
mmol/L
2.2-2.7
2.2-2.5
protein, total
mg/dl
5.4-7.8
5.4-7.8
chloride
mEq/L
95-125
105-129
sodium
mEq/L
139-154
140-158
cholesterol
mg/dl
125-270
95-140
triglycerides
mg/dl
29-291
cholesterol, SI
mmol/L
2.5-5.9
2.1-4.3
trypsin-like immunoreac-
tivity (TLI)
ug/L
5-35
creatinine
mg/dl
0.5-1.5
0.5-2.0
Vitamin B12
pg/ml
175-550
creatinine, SI
mmol/L
3.5-7.1
5.910.5
globulins
g/dl
2.5-4.7
2.6-5.0
creatine phosphokinase
(CPK)
IU/L
20-400
20-400
unconjugated bilirubin
mg/dl
0.1-0.6
0.1-0.2
glucose
mg/dl
65-120
70-145
glucose, SI
mmol/L
3.9-6.1
3.9-8.0
SI values collected from several sources but most are either calculated from our normals or are from the Handbook of Small Animal Practice, Morgan, 2002
Blood Cell Count and Blood Cell Examination Values
Cell Value
Units
Dog
Cat
Red Cell Values:
hemoglobin (hgb)
g/dl
12-18
9-15
hematocrit (HCT)
%
32-54
28-42
Red blood cell count (RBC)
#/ul in millions
5.5 - 8.5
5.5 - 9.0
Nucleated Red Blood Cells (nRBC)
#/100 white blood cells
<1
<1
Packed Cell Volume (PCV)
%
32-54
28-42
Platelets
#/ul in thousands
Reticulocytes
%
0.2-1.1
0.1-0.5
MCH
pg
19-25
13-17
MCHC
g/dl
32-36
30-36
MCV
fl
60-77
40-55
White Cell Values:
Total White Blood Cell Count
#/ul
5,500 - 17,000
5,000-19,500*
Neutrophils (polys, PMNs, Segs)
%
62-78
60-78
#/ul
3,500-12,000
3,500 - 17,000
Band Neutrophils
%
0-3
0-3
#/ul
0-300
0-300
Basophils
%
0-1
0-1
#/ul
0-10
0-10
Eosinophils
%
0-3
0-3
#/ul
0-800
0-800
Lymphocytes
%
12-30
17-32
#/ul
1000-5000
1500-7500
Monocytes
%
0-1.5
0-1.5
#/ul
100-1350
50-850
Blood Coagulation / Inflammation Indices:
d-dimers
<250
<250
fibrinogen
mg/dl
200-400
100-300
prothrombin time
seconds
6-12
6-11
partial thromboplastin time (PTT)
seconds
10-25
10-25
mucosal bleeding time
minutes
<4
<5
Immunology
Test
Units
Dog
Cat
Antinuclear Antibody (ANA)
titer
<1:40
<1:40
Rheumatoid Arthritis Factor (RA Factor)
titer
NEG
Coomb's Direct
NEG
NEG
Lyme Disease
titer
<1:64 (NEG)
<1:64 (NEG)
Rocky Mountain Spotted Fever
titer
<1:64 (NEG)
<1:64 (NEG)
Ehrlichia canis
titer
<1:20 (NEG)
<1:20 (NEG)
Parvovirus (protective titer)
Hemagluttin-inhibition
(HI titer)
>1:80
Canine Distemper (protective titer)
Serum Neutralization Titer (SN titer)
varies by laboratory
Feline CoronaVirus
(feline infectious peritonitis)
Titer
varies by laboratory, positive only indicates exposure to coronavirus NOT FIP
It is important to note that protective titers for evaluation of resistance to disease are considered unreliable by most immunologists at the present time. Titers measure antibody response and this is only one part of the immune system's role in fighting disease. This is particularly true for the newer recombitant vaccines, which may not stimulate titer rises but still confer immunity by stimulating other portions of the immune system. At the present time it is probably better to rely on duration of immunity data as it is collected for various vaccines than to rely on titer measurement as a way of determining when to booster vaccinations.
Therapeutic Drug Monitoring
Medication
Units
Dogs
Cat
Notes on Testing:
Phenobarbital
(therapeutic dose range)
ug/ml
15-45
*25-45 if seizures persist15-45
Takes 2 to 3 weeks to stabilize after initial dosing, test 4 to 6 hrs after morning pill, retest at 6 month intervals. If seizure control poor consider testing after 12 hours to see if the trough level is too low
Primidone
ug/ml
15-45
15-45
Test for phenobarbital levels as advised above -- this is the active ingredient
Thyroid hormone
dog = supplement
cat = post methimazole
ug/dl
1.5-3.5
1.5-5.0
Dogs- test 4 to 8 hours after morning thyroid supplement, retest every 6 to 12 months
Cats - test after 1 to 2 weeks of methimazole administration, retest every 3 to 6 months
Digoxin
ng/ml
0.9-3.0
0.9-2.0
Test 2 to 5 hours post pill but this varies, so if toxicity is suspected repeat at 8-10hr
Bromide alone
mg/dl
mg/ml
150-200
1.0-2.0
Test anytime during day, test after 30 days of use, then every 3 to 6 mo
Bromide with phenobarbital
mg/dl
mg/ml
200-300
2.0-3.0
Test anytime during the day, test after 30 days, then every 3 to 6 months