Feline Laboratory Tests

Feline Laboratory Tests

High Calcium Levels

Question: Dear Dr. Richards,

I am a new subscriber and already have a question regarding my very loving kitty.. Cocoa.

After some blood and urine work, my vet has informed me that Cocoa's calcium level is high (13.8), indicating that he may have some kind of cancer. I'm in shock and am scared to death that I may lose him so I've been searching the net for more information. Unfortunately, I haven't found very much out there and what I have found does not sound very promising.

The vet suggested we also do a parathyroid test as it may be the cause of his elevated calcium but we won't have the results till next week. I can't find anything on the net about the parathyroid. If nothing shows on this test, the vet has suggested we do an ultrasound.

The other readings which have variances include:

CGT at 0 (normal range 1 - 7)

BUN at 48 (normal range 15-34)

Creatinine at 2.6 (normal range 0.8 - 2.3)

WBC at 4.2 (normal range 5.5-19.5)

MCH at 13.0 (normal range 13.3 - 17.5)

MCHC at 29.6 (normal range 31 - 36)

onocytes at 5 (normal range 1-4)

Absolute Lymphocyte at 966 (normal range 1500-7000) E

verything else is in line with normal ranges.

He is eating very well but seems to drink a lot of water. I've been giving him fluids about every 2-3 days and that has really helped his thirst.

My question is... is there any way the vet could be wrong? Should we do another round of blood and urine work? What percentage of cats with this kind of calcium level actually have cancer?

Please help.. I'll be lost without him. Thank you. Regards, Karen

Answer: Karen-

In dogs, high calcium levels in the blood stream are most commonly associated with cancer, especially lymphoma. In cats, high calcium levels associated with cancer do occur. Some sources say that cancer is the most common cause of high calcium levels in cats but I think that the most common current view is that high calcium levels in cats is just about equally likely to be due to chronic renal failure. In a study by Savary, et. al., reported in a recent issue of the Journal of Veterinary Medicine, stones in the urinary tract (uroliths) were also a common cause of high calcium levels in cats. Lab error and primary hyperparathyroidism are the other causes of high calcium levels in cats. It is important not to overlook lab error as a possibility before making any decisions based solely on high calcium levels in the blood stream.

Checking carefully for any evidence of calcium oxalate stones in the urinary tract (X-rays usually show these stones if they are present), rechecking the serum calcium level, using an ionized calcium test, if possible, would also be a good idea. The ionized calcium more accurately reflects the "real" calcium level in the blood stream and can help your vet distinguish between the possible disorders that lead to high calcium. Checking the parathyroid hormone levels is also a good idea, so your vet is ahead of the curve having already sent off for that test. In cats, the parathyroid glands are enlarged enough to palpate when there are parathyroid tumors, so feeling the neck region for evidence of lumps is a good idea, too.

There is enough elevation in the kidney values reported to make kidney disease a real possibility in your cat. While this isn't as good as nothing being wrong, as would be the case with a lab error, it is better than cancer. There is a lot of information on our site and on the feline chronic renal failure site we have a link to on our link page and reviewing that would be a good idea.

It is hard to be patient and wait for lab results but it is necessary. Keep working with your vet to sort through this problem. I am hoping the outcome will be better than you are fearing.

Mike Richards, DVM

Blood pressure monitoring

Blood pressure monitoring in dogs and cats will become more common as time goes on. At present there are some problems with equipment and there does not seem to be a clear consensus on blood pressure normal values.

It is harder to measure blood pressure in dogs and cats than it is in humans because of the variances in size, anatomy and willingness to sit still and allow the process to take place. There are three methods for obtaining reasonably accurate blood pressure measurement.

The oldest and most accurate is placement of a catheter directly into the artery and direct measurement of the pressure using a manometer. Most vets are not really anxious to place arterial catheters in patients for routine monitoring of blood pressure.

Two methods of "indirect" blood pressure measurement are also used. One uses a Doppler system and the other an oscillometric system. The oscillometric system is probably more accurate but doesn't work well for pets weighing less than fifteen pounds making it impractical for use in most cats and many small dogs. It measures both systolic and diastolic pressure. The Doppler system only measures systolic pressure. It can be used in any size patient but is not considered to be as accurate and requires a trained operator.

The definition of hypertension varies from reference to reference. Dr. Morgan's "Handbook of Small Animal Practice" lists the range for normal arterial blood pressure as 130 to 180 for systolic pressure and 60 to 100 for diastolic pressure and makes no distinction between dogs and cats. I have seen references that suggest that anything over 120 may be hypertension in the cat and that the high end of normal systolic pressure in the dog may be as high as 210. Blood pressure is known to vary among breeds of dogs and that may explain some of the reported differences.

Blood pressure devices cost between $900 and $3500 new. It is possible to buy oscillometric units used from the human market and modify the cuffs for pets but the savings aren't all that great after doing that and the machines are more sensitive to the human blood pressure ranges which are lower than those of pets making them a little more inaccurate for vets. To be able to monitor blood pressure with reasonable accuracy the cuffs must be correctly sized.

One of the problems with veterinary medicine is that this cost must be recovered in some manner and the office visit price is usually competitive in veterinary medicine so that isn't a good place to make it up. But people are used to having their blood pressure taken as part of an office visit at their doctor's so a separate charge can be hard to justify, too. So vets are buying one or two machines that are probably not going to be money makers and for which the accuracy is a little questionable and normal values hard to find. Many vets, looking at all of this, opt not to buy the machines.

Mike Richards, DVM

What's a titer

Q: Dear Mike, What causes Titer? My Cat tested Antibody Present 1:6400 Yet none of the other cats (#in 100s) test positive for FIP, from cattery. Only symptoms - weight loss +dehydration =1.3 lb. vomiting 5 times three months small amount of sleep in eyes. I changed diet to yogurt, - boiled rice & chicken, - and I am forcing water. He is eating these things in quantity like normal within 2 days. Please help! R.

A: A titer is a measurement of the dilution level at which antibodies to a disease are still detectable during testing. The titer values are used to determine the likelihood of a disease. Titers for the same disease can vary from laboratory to laboratory depending on how they run the test. Titers for different diseases are not comparable at all -- a titer of 1:20 is significant in some diseases while a titer of 1:6400 may be "normal" for another disease. When interpreting titers it is very important to know what the testing lab considers the normal levels to be and to consider factors about the disease that may influence the titer.

For feline infectious peritonitis (FIP) there are several factors to consider when looking at titer levels. In most labs, titer levels of 1:1600 or less are considered to be normal (or below the range where active infection is likely based on serology alone). It is also important to consider the number of cats living in the household with a cat you are testing for FIP. In multi-cat households the "background" titer level is likely to be higher in a cat for FIP than it is is a one or two cat household, since exposure to coronavirus (the type of virus that causes FIP and other enteric infections in cats) is going to be more likely. So a cat with a titer of 1:6400 in a household with many cats is less likely to actually have FIP than a cat living alone with a titer this high. In catteries it is possible that 1:6400 should be considered the "suspicious" level for titers. The last thing you have to consider is how sick the cat is. In a very sick cat with a lot of signs of FIP (dehydration, fever, weight loss, lethargy, enlarged abdomen, etc.) a low titer level has to be taken more seriously than in a cat that isn't sick. It can be a difficult interpretation in this situation but that is what you pay your vet for, so make him or her tell you what it means to them. It can be useful to check the titer again in two or three weeks in these cases. A rising titer would be meaningful and a falling titer in the face of the illness worsening may be indicate a very bad short term prognosis.

Titer levels above 1:3200 are usually considered to be sufficient to suspect FIP so you do have to take the titer seriously but this test is inaccurate enough that you should almost never base a diagnosis on titer alone. Interpreting the result in light of your cat's individual situation is very important. Again, this is something you should talk to your vet about and your vet should take the time to tell you what the result means for your individual cat.

Mike Richards, DVM
Testing for Kidney failure
Q: Hi- I have a 16 yr. old cat who has always been very healthy. A couple days ago, I noticed that she seemed a little sluggish and just not quite herself. Then she seemed to be having difficulty walking, every movement seemed to be an effort and her breathing seemed very labored.
I chose a Vet who comes to the home, to avoid any stress to Goldie. He looked in her mouth and ears and listened to her heart. He said that she has kidney failure as a result from feline leukemia, is enemic and therefore very weak.
I am wondering if such a diagnosis can be made from the small exam he gave her? Also, Goldie has not been in contact with another cat since 1988. How could she have contracted the disease?
Lastly, the Vet said she is in the last stages, there is nothing to do except make her comfortable and watch for signs that would indicate she is suffering. He did prescribe a Steroid to give her a little more energy. Could she already be in the last stages without ever exhibiting any symptoms? If his diagnosis is correct, is this indeed all that can be done?
Obviously, I need answers as soon as possible so I can be doing the right thing for Goldie.
Thank you for your time
A: Dear Donna
Unless the vet did labwork at your home it is not possible for him to diagnose either kidney failure or feline leukemia from an exam alone. There are blood and saliva tests for feline leukemia which could easily be done by a house call veterinarian at the home. There is also a small portable blood analyzer made for house call veterinarians but some blood would have to be drawn to do the tests.
Prior to the availability of good lab machines for use in the clinic and now even for house calls, I used to think that I was pretty good at diagnosing kidney failure from clinical signs in cats. When it became possible to test them quickly enough that I could test prior to treatment I discovered that much of the time my presumptive diagnosis of renal failure was incorrect in older dehydrated cats.
I think it would be a good idea to get a second opinion.
Mike Richards, DVM
Positive ELISA
Q: My kitten had a positive ELISA test today and I am going crazy thinking about what this means. My vet told me it does not look good. Please tell me what the chances are of a false positive. I can only hope but I can't bear the thought of losing my baby.
A: Dear Julia
The possibility of a false positive test would depend on what was being tested for. Feline leukemia virus tests are pretty accurate but probably have false positive results one to four times per 1000 tests. The feline leukemia tests are usually directly for viral antigen. Some kittens can probably fight off the virus completely and many others can suppress it sufficiently to keep it out of the bloodstream and not be affected by the virus unless they experience later immune suppression for some reason. It is always a good idea to retest 3 weeks or more after a positive feline leukemia test to see if the kitten has become negative. I think that the false positive rate is higher when using saliva or tears for testing than when blood is used.
Feline immunodeficiency virus tests are more likely to be false positive, especially in a kitten. This test is for antibody and maternal transfer of antibody can occur. This gives a positive test result and the kitten may not be infected.
Feline heartworm tests using an antigen detecting system have false positive rates similar to feline leukemia tests. Feline heartworm tests that detect antibody to the heartworms have an unknown false positive rate because no one really knows how many cats are exposed to heartworm larvae without ever becoming infected. A positive heartworm test in a cat should be evaluated in conjunction with the presence of clinical signs or other test results such as X-ray changes or ultrasonic identification of heartworms. Your kitten probably had a feline leukemia test since it is done most frequently in kittens of these tests. Retest when your vet thinks it is best to do so and if the second test is positive consider having that confirmed with an alternative test such as IFA testing. If your kitten is still positive you will have to make plans to deal with that situation.
Mike Richards, DVM
Last edited 01/30/05


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...