As much as we would like to have a test that could be run on a single drop of blood, answer every medical question that could possibly arise, and cost less than ten dollars, we’re not there yet.
Or, anywhere close.
The most common panel of screening lab tests for general, overall health status includes:
• complete blood count (CBC), that tells us how many red and white blood cells a patient has.
• differential, part of the CBC, which shows how many of each different type of white blood cell is present.
• chemistry profile (chemistries), which conveys information on the major organs (liver, kidneys, pancreas), blood sugar and electrolytes (sodium, potassium, chloride, bicarbonate, calcium, phosphorous).
• urinalysis, which has a chemical part (ph/acidity, concentration, protein, sugar, etc.) and a microscopic part (bacteria/infection, bladder cells, kidney cells, blood cells, crystals that might contribute to stone formation, etc.)
The above collection of tests is sometimes referred to as a “minimum database,” or the smallest collection of tests that will give us a good overview of a patient’s health. This panel might be requested for screening before anesthesia, or a pet ill with non-specific signs.
A common question pet owners ask about minimum database results is, “If he has cancer, will it show up on that test?”
The answer is…maybe. But, probably not.
If a pet is suffering from leukemia, a cancerous proliferation of white blood cells in circulation in veins and arteries, it will be evident on the CBC.
Patients with bladder cancer might have abnormal cells show up on the microscopic portion of the urinalysis. I emphasize “might.” The mass will have to “shed,” or give up, cells into the urine at the time the sample was obtained. Such shedding is an intermittent process.
When our patient, Scottly, had bloody urine recently, the laboratory found cancerous transitional cells on the microscopic portion of the urinalysis, which led us to obtain special contrast radiographs (X-rays) of the bladder, outlining the mass we could not palpate because of its hidden location.
An indicator of some, not all, kinds of cancer can be an elevated calcium level in the blood. Lymphoma patients often exhibit this abnormality.
However, tests for specific cancer “markers,” signature protein compounds produced by some cancers, are expensive to test for, and generally beyond the budget of most pet owners.
In one instance, a pet owner asked if a blood sample taken for a heartworm test would show the breeds their mixed dog consisted of.
Another asked if the heartworm test would tell why his dog throws up intermittently.
“Since heartworms don’t make dogs vomit, and this is a ‘yes-or-no,’ ‘does-he-have-heartworms-or-doesn’t-he’ test, it won’t tell us about vomiting.”
Or, breed DNA.
Some blood tests are just that specific, and tell us about one specific parameter in the body.
Until the day the universal blood test is invented, we will continue to order panels and individual tests each patient’s needs call for.