There are a
number of factors which may affect test results. This page discusses these factors, such as whether it is necessary to fast
a cat before blood tests.
gives a rough idea of normal ranges for tests commonly run on CKD cats,
and explains why there are differences between various laboratories. It
also has veterinary links explaining more about test results.
Ranges for test results differ between the USA and the
rest of the world. This page explains those differences.
Factors That May Affect Test Results
Certain factors may affect test results, and in certain cases may
make the results somewhat inaccurate. Stress, fasting before a test, or
how the test is handled by the laboratory may all have an effect. This
section covers some of the more commonly seen issues.
If cats are not
fasted before blood draws, then lipaemia may occur, particularly if the
cat has eaten a meal rich in fat. This means that lipids (fats) are
suspended in the blood, which may make the sample thicker and harder to
lipaemia is relatively rare in feline blood samples, and even if it is
present, it is unlikely to make a major difference to the test results.
Therefore it is not
usually necessary for a cat to fast before the usual tests for CKD, and
overall I think it is a bad idea because an empty stomach can increase the
risk of excess stomach acid. Also, cats who are being fasted simply do not
understand why we won't feed them, which is stressful for them, especially
if other family cats continue to get fed whilst they do not.
certain specialised tests, such as those for
parathyroid hormone or pancreatitis, fasting for twelve hours may be
necessary; be guided by your vet.
I have heard of
some vets asking that people not give their cats fluids for a day or two
(in one case, a week!) before bloodwork. I do not understand this: since
the cat normally receives fluids, surely you will obtain more accurate
results, reflecting how the cat's bloodwork normally looks, if the cat has
his/her usual levels of hydration.
I do recommend
that you try to be consistent i.e. always have the tests done before
sub-Qs or after sub-Qs, at the same time of day if possible.
Stressed Cats or Cats Who Fight Blood
If your cat
fights at the vet, or gets very stressed, this may have an effect on some
of the test results. For example, blood
glucose levels are often
raised in stressed cats, so they do not automatically indicate that
diabetes is present.
CPK, a muscle enzyme, may be raised because of a bad blood draw.
bloodtest results will mention that they are haemolysed. This means the
blood cells being tested have ruptured, often as a result of poor
should not have any real effect, but a grossly haemolysed sample may
affect results, causing some values
to appear higher than they are and others to appear lower:
appear higher than it is
appear lower than it is
usually appear higher than it really is, but occasionally it will appear
If a sample has
been haemolysed, you might wish to ask your vet to take new blood samples
and run the tests again.
(2003) Arzoumanian L Becton Dickinson Tech Talk 2(2) pp1-2
has more information on haemolysed samples.
Platelets are the component of blood which causes it to clot. If they were
not present, we would bleed to death whenever we got cut.
Unfortunately when a sample of blood is taken, some of the platelets may
"clump" (stick together), especially if the blood sample is not mixed with
the anticoagulant immediately. Clumping platelets are extremely common in
cats - they occur in as many as 75% of cat blood draws. They are
even more likely if it is difficult to get blood from the cat. Taking them
from a leg rather than from the neck may also be a factor.
The clumping means that it can be difficult to count the platelets
accurately, which in turn means that the number may appear low. However,
you may sometimes see platelet counts listed as low, followed by a comment
that the platelet estimate is "adequate." This means that the person
running the test could not tell the platelets apart enough to be able to
count them, but could see that overall there are enough.
If a cat truly has low platelets, then you may see increased bleeding e.g.
from the nose, gums or in urine.
Pet Place has some information about low
Between US and International Measurement Systems
uses the SI system (Systčme Internationale D'Unités) as its measurement system,
apart from the USA.
Although I am
familiar with both systems, having lived in both the UK and the USA,
Tanya's Feline CKD
Support Group has primarily American
members, so you will get more feedback when you join if you post your
results in American values.
units in the international system are:
millimole per litre.
The SI unit in medicine for measuring concentrations of substances in the
micromole per litre. This is 1000 times smaller than mmol/L. So for example 1
mmol/L is the same as 1000 µmol/L.
Since not everybody can access the µ symbol, sometimes you will see umol/L
This measurement is used for creatinine and some other values.
This is grams
It is not part
of the SI but is often used for some reason for urea in France and
Commonly used units in the US system (which are also sometimes used in
some European countries) are:
deciliter, the unit used in medicine to measure the concentration of
substances in the blood.
1 mg/dl equals
0.01 grams per liter (g/L ).
Milliequivalents per liter.
This is normally used for potassium.
the values are exactly the same as those expressed in mmol/L.
into BUN (Especially from French Measurements)
The USA usually measures blood urea nitrogen or BUN. Most other countries
When converting urea from your international results, choose BUN or blood
urea nitrogen from the dropdown menu - that is the nearest US equivalent.
Normally if you are converting from international to US values, you are
converting from mmol/l to mg/dl. However, in France and Portugal the measurements are
often in g/l but as is usual in Europe, they are for urea, rather than BUN.
You have to do some quite convoluted calculations to obtain the US BUN
Abbott Laboratories(2016) Abbott Laboratories Abbott Point of Care says:
"To convert a BUN result in mg/dL to a urea result in mmol/L, multiply the
BUN result by 0.357. To convert a urea result in mmol/L to a urea result
in mg/dL, multiply the mmol/L result by 6. To convert a urea result in
mg/dL to a urea result in g/L, divide the mg/dL result by 100."
You actually want to do things the other way around. Here is the formula.
Take your urea value in g/l
Multiply by 100 to get the mg/dl result for urea
Then divide by 6 to get the mmol/L value for urea
Then divide by 0.357 or multiply by 2.8 to get BUN in mg/dl
I did this with Thomas's extremely high 86 mmol/l urea level (BUN of 241)
Urea value 5.16 g/l
5.16 g/l urea
Multiply by 100
516 mg/dl urea
Divide by 6
86 mmol/L urea
Divide by 0.357 or multiply by 2.8 to get BUN
241 mg/dl BUN
you can replace the last two steps by simply dividing the urea mg/dl (516
in this case) by 2.1428 to obtain the same result (241 in this case). This
also applies if you are given urea in mg/dl and wish to convert it to BUN
Rapid Critical Care Consult will do the
calculation for you, which is a lot easier.
Click on urea, then click on the dropdown menu next to it that says mg/dl
g/l if you are in France or Portugal and have your results in g/l.
Choose urea and mmol/l if you are in the UK or other countries using
mmol/l. Choose urea and mg/dl if you are in Germany or other German
speaking countries which list urea in mg/dl.
The Nephron Information Center
has an excellent converter so you can convert your measurements as
Remember to click on the SI/L button, and to convert urea to BUN.
You cannot compare tests performed by different laboratories or even those
performed on different machines. So if, for
example, your vet does tests in-house but also sends them out to an external
laboratory, you will probably find the results differ.
The quality of veterinary in-clinic and reference
laboratory biochemical testing (2012)
Rishniw M, Pion PD & Maher T Veterinary Clinical Pathology41(1)
pp92-109 states "caution is needed when comparing results obtained by
different methods in the in-clinic and reference laboratory, and knowledge of
the methods used for analysis is imperative."
Reference ranges also
differ from laboratory to laboratory.
Reference ranges are not uniform because of the way they are created. They are
created by each laboratory by taking samples from animals who are known to be
healthy. They then use these to create a range that in theory represents about
95% of healthy animals. Each laboratory does this differently.
IDEXX is one of the big reference laboratories and your vet may send blood out
to them for testing. However, if you see IDEXX ProCyte (or Catalyst DX or
VetTest) on your cat's results, this normally indicates that your vet is using
in-house testing equipment. The machines are calibrated for that laboratory's
reference range but there may be some differences.
Generally speaking, reference laboratories are more accurate. This may be in
part because they recalibrate their equipment more frequently (though some
machines recalibrate automatically these days) and their staff
are more skilled at reading results.
In-house versus reference lab testing part II
(2011) Antech Diagnostics Antech InsightsSep 2011 pp1-7
found that most blood chemistry results from in-house tests were accurate, but
there could be problems with the CBC (checks for anaemia or infection).
Personally I view the ability to do tests in-house as a blessing. I
remember one horrible long holiday weekend years ago when we had to wait three
days for test results from a laboratory to be done, and in the meantime we
could not offer our cat anything other than supportive care in hospital. My
own feeling is that I like to know what I am dealing with as quickly as
possible, so we can get started with a treatment plan. I do not worry too much
about results if they are being done in the same way (e.g. always run on the
same machine at the vet's) but if you are concerned, you can either always
send out your cat's tests to a lab, or do so if they do seem out of sync in some
Normal Ranges for Blood and Urine Tests:
These ranges are
approximate - if those your vet provides are different, which is
quite likely, you should be guided by them. I am providing them here just
to give you a very rough idea.
These ranges are also not directly comparable. For example, the
upper limit for urea/BUN is noticeably lower in the SI system.
This table contains indicative ranges, but that does not necessarily mean that a
result within these ranges is acceptable. For example, a CKD cat should
aim for a phosphorus level no higher than 4 (US) or 1.3 (international),
while most CKD cats do better if their potassium level is around 4.4.
Pet Place explains how to take your cat's
Heart and Respiration Rates
there appears to be little agreement on what is normal in terms of pulse
and respiration, as the table below shows.
Feline cardiology (2011) Côté E,
MacDonald KA, Meurs KM & Sleeper MM Wiley-Blackwell gives reference
ranges for heart and respiration rates for cats and kittens both at home
and at the vet's.
whose cats have heart problems learn how to use a pediatric stethoscope on
their cats. Even if you don't do this, ask your vet for guidance on what
is normal for your cat.
If your cat
appears to be having trouble breathing, i.e. an increase in breating effort
or breathing rate, particularly if s/he breathes with the mouth open, it
is a medical emergency and you should seek veterinary help immediately.
are normally measured when the cat is asleep or at least resting. They will always be more
frequent when the cat is awake. Breathing in and out once counts as one
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
If your cat
appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
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