April Post

About a month or two ago, a report was published by a U of C professor suggesting that the routine use of PSA (prostate specific antibody) screening test in men may cause more harm than good and as I listened to him being interviewed on the CBC, it seemed he made very reasoned and well substantiated arguments why this test should not be part of routine diagnostics.

The very next day, a doctor from the Prostate Cancer Center was also interviewed on the CBC and he made very reasoned and well substantiated arguments for why the PSA should be a part of routine diagnostics.

More than likely this is not a new story, although the test in question may be different. Pap smears, mammography and any number of screening tests have also been scrutinized with such a jumble of outcomes that sometimes it’s difficult to know what anyone ought to do.

The premise of screening tests is simple. Take an individual who is not experiencing any problems, diagnose them early, treat them quickly and they should have a better prognosis.

So when you hear debates about the usefulness of any test, the challenge for any researcher is determining whether that test improves total health outcomes (or not) in a large population. Although stories of individuals who have been saved or harmed on the basis of routine screening are interesting, that’s not how we’re supposed to look at these tests. If a test saves 20 people but winds up with 100 experiencing a major complication, then you would have to conclude that this test is not worth doing.

So how does that relate to veterinary medicine?

There are a few common screens done in veterinary medicine. Heartworm tests, fecal examinations, pre-operative blood test and senior screens are just a few worth noting.

Some will argue that some of these don’t really qualify as screening because we assume these patients into high risk categories. Senior cats do have a high risk of kidney disease, dogs who live in or travel to high risk heartworm areas will have higher risk of having heartworm. While we can debate the merits of these suggestions, I would like to focus my attention on pre-anesthetic blood tests for young (apparently healthy) pets. For some of you, we have had this discussion before but I think it’s worthwhile to put my opinion on paper.

It is common practice for many veterinarians to insist on routine pre-anesthetic blood tests in all patients. The reason is that since drugs are often eliminated through the liver and the kidneys, any dysfunction of those organs could compromise the safety of the anesthesia.

That used to be the thought process for humans as well but ask any human anesthesiologist and they will tell you that’s not entirely true. In fact, it’s actually quite rare for a human anesthesiologist to insist on blood tests for their low risk patients. The problem is that young healthy patients rarely have kidney and or liver problems so in order to find one person who is actually ill, you need to test hundreds. The other problem is that sometimes when you run a test there’s a probability that in spite of being “abnormal” on the blood test, there really isn’t anything wrong. There may be a lab error, there may be an actual abnormal result which isn’t repeatable or you may just be an outlier (you are normal and healthy even though your blood test consistently tells you otherwise).

Dogs and cats are not little people though and we rarely anesthetize young people unless they have a problem. We routinely anesthetize young healthy animals and in many cases they haven’t been alive for long enough to manifest whatever illness they may be battling. Besides that, dogs and cats don’t speak and most animals are instinctually conditioned to exhibit normal even when things are not.

So where does that leave us?

In my opinion, a young healthy dog or cat is suitable for anesthesia with or without blood testing. I understand the notion of unknown risk but I really don’t believe we are compromising the welfare of our patients when we go forward without diagnostic tests.

On the topic of risk, it’s also very important to consider that blood collection is puppies and kittens can be a very stressful ordeal and has the potential to create long term anxieties at the vet.

I would be happy to compare my anesthetic outcomes with anyone.

Those that believe that they cannot safely anesthetize a patient without blood tests are equally right.

Someday, someone will move forward with a study to prove one of us wrong. Until that day comes, remember that a collection of opinions does not make a fact.

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