Reading the Blood Chemistry Panel: An Art and Science

Ever wonder what are the normal values for blood chemistry elements for dogs (and cats)? Well, actually "normal" is quite relative. Each veterinary diagnostic lab and "in clinic" laboratory equipment will have its own "normal values" calibrated to standards, so variations in what are called "normal values" should be expected.

The blood chemistry panel is a vital tool in the diagnosis of dog (and cat) diseases. An essential part of a thorough evaluation, most animal hospitals have provisions for evaluating blood chemistry values for dogs (and cats) either on site or via a local veterinary diagnostic laboratory. Newer instrumentation and techniques for evaluating blood chemistry make the use of the information gained from a blood chemistry panel a standard of practice.

There are a number of different metabolic parameters that can be evaluated, and when tied in with other diagnostic entities such as a urine analysis, radiographs (X-rays), physical exam and patient history, an accurate picture of a patient's health status can be assured.

Veterinary medicine, like medicine in general, is truly an art as well as a science. Looking at scientific data alone and turning a cold shoulder to the art will lead any healer astray. Accurate interpretation of scientifically acquired data requires introspection, experience, and a thorough evaluation of the physical and emotional aspects of the patient. Only after combining the two -- the scientific, cold, unemotional facts with the “hands on” evaluation of the entire patient -- will the doctor be enabled to make a proper diagnosis. And for any effective therapy to be instituted, an accurate diagnosis must be established first.

Laboratory Analysis

Canine patients of today have a distinct advantage over their predecessors of a few decades ago. Back then, veterinarians had only a few rudimentary tests for blood chemistry components at their disposal.

Today many veterinary clinics have “in house” blood chemistry analyzers that provide a wide variety of information in a matter of minutes. Other clinics rely on local veterinary laboratories that will pick up blood samples and fax or phone the results back to the clinic the same day. This state of the art of veterinary practice was only a dream a few years ago -- now routine blood chemistry evaluation is a standard of practice in every clinic.

The Chemistry Panel

When the patient’s blood is drawn the sample is allowed to clot, then the clear fluid is extracted -- without the fibrin, red and white blood cells, or platelets. Serum, as it's called, is what is presented to the lab for an evaluation of a number of chemicals circulating in the patient’s blood. Each laboratory, including the veterinarian’s "in house" lab, will establish normal values for dogs and other species. The analyzing instrument checks for amounts of these chemicals, which is then generated as printout with the patient's values compared to "normal" values.

Once the scientific data is in the doctor’s possession, the art of veterinary medicine comes into play. (Doctors are taught to “Treat the patient, not the paper”.) For example if the blood value for a chemical that reflects kidney function, such as creatinine, seems to be present in amounts higher than normal, does that unfailingly indicate diseased kidneys? And what if the sodium level seems a bit too high, does that mean there are dysfunctional kidneys or a hormonal imbalance? Or is the dog simply dehydrated because the owners forgot to provide water the previous 18 hours?

The art of medicine requires the practitioner to mentally view the entire canvas of possibilities even before the final painting is fully visible. And because there are so many variables affecting the blood chemistry, many veterinarians require a urine sample to be evaluated at the same time as the blood chemistry is submitted -- otherwise the reliability of indicated abnormal results may be questionable.

Mark Hitt, DVM, MS, a veterinary specialist (Diplomate of the American College of Veterinary Internal Medicine - Specialty of Internal Medicine) practicing with the Atlantic Veterinary Internal Medicine group in Annapolis, Maryland, underscores the value of utilizing the Blood Chemistry Panel by citing an interesting case. The successful management of this dog’s medical difficulties would have been doubtful if a chemistry panel was not performed.

Hitt relates:

"Hans, a ten year old Doberman, had been seen by his referring veterinarian with the goal of a general health evaluation and potential teeth cleaning because of bad breath. The owners allowed the pet’s veterinarian to run a chemistry profile, CBC, and urinalysis a few days prior to the proposed anesthesia for the dental procedures. Neither owner had been alarmed at the gradual, mild decrease in Hans’s appetite, weight, and vitality. They had presumed he was "just getting older.'

When the blood chemistry results were reported there were several abnormal values that related to liver disease (ALT, ALP, bilirubin). And, the red blood cell count was low suggesting an unsuspected anemia was present. These findings led to referral to our center for further tests to assess the liver’s function (serum bile acids), size (radiographs), and textures and patterns (sonography).

A large lump was found in one lobe of the liver. This was biopsied without major surgery by using an ultrasound guided needle biopsy technique. A pathologist examined the sample of liver tissue and the assessment was that this patient had a non-malignant form of cancer called a canine hepatoma.

Although there was the concern that a more malignant cancer could be present despite the pathologist’s best assessment, the owners wanted to proceed. Hans was transferred to our surgery group to remove this lobe of liver and to examine the other organs. The surgeons commented that the tumor (Latin for a “swelling”) had been bleeding internally and was in danger of rupturing completely at the time it was removed.

After the surgery the dog’s liver enzymes returned to normal as did his appetite, weight, and energy levels.

Not every case is as dramatic, or has as positive of an outcome, as this case. But it does highlight the importance of routine examinations and testing in older patients. Eventually, Hans did have his teeth cleaned. There are many other similar cases that I have seen where kidney, liver, hormonal, and other medical problems have been detected early through the help of the blood chemistry panel."

Hitt goes on to state that statistically about 1 in 20 tests may be abnormal without truly being relevant. In other words, a dog may have, for example, a higher than normal liver enzyme value for long periods of time and yet be a healthy individual.

"The medical significance of an abnormal test result," Hitt said, "can only be assessed by the veterinarian when the patient, patient history, and degree of value change are kept in mind. And, if a test result is considered significant, it may lead to additional tests for either confirmation of a problem’s significance to the pet or for further information relating to the concern."

Suggestions for Dog Owners

Whenever you find yourself in the veterinarian’s office with a sick dog, be proactive and ask the doctor if doing a blood chemistry evaluation would be helpful. You’d want it done for yourself, wouldn’t you? And expect that a blood chemistry profile would be required prior to any elective anesthesia or surgery. You’d be surprised how many elective procedures are put off until the reason for a previously unnoticed medical problem is evaluated.

Many animal hospitals are providing annual Older Pet Evaluations where results of blood and urine testing are vital in making a proper health evaluation of the patient; so if your dog is eight years of age or older an annual physical exam with laboratory tests can be a very rewarding practice.

Price

An informal survey shows that for a routine blood chemistry panel the dog owner might expect to pay from $17.50 to over $60.00. One reason for the variation in price is that some chemistry panels check for a wider array of values than others. The price reflects the veterinarian’s time and costs in collecting, sending, interpreting the results and a discussion of the report with the dog owner.

Always ask what the cost is but do not be reluctant to have this extremely important laboratory evaluation done. Dr. Hitt adds, "Remember, the most value from a chemistry panel may be obtained when combined with a urinalysis (UA) and a complete blood count (CBC)." The science is necessary for the art to work properly!

A typical blood chemistry panel might include the following tests:

Normal values for blood chemistry elements for dogs (and cats) are displayed in the table below. Keep in mind that each blood chemistry machine and every veterinary diagnostic lab has their own set of normal values calculated for their particular instrumentation.

The values shown here may be different from normal ranges your veterinarian refers to when making judgments about patients' reported blood chemistry values.

Normal Ranges for a Laborator's Blood Chemistry Values

Dogs

Cats

HEMATOLOGY: Normal ranges for blood cell elements for dogs (and cats) are displayed in the table below. These values are approximate and may not be the "normal" values established for any other individual veterinary pathology lab or blood analyzer.

Normal Ranges for a Laboratory's Hematology Values

Dogs

Cats

 Image: Neeta Lind / via Flickr