WHEN “ABNORMAL” IS OK
When any labwork is done on your horse, his results will be compared to a “normal” range. “The general process to figure out the ‘normal’ range for most of those tests is to gather as large a number of healthy horses as you can and run bloodwork on all of them,” says Katherine Wilson, DVM, DACVIM, of the Virginia– Maryland Regional College of Veterinary Medicine. “Usually about 95 percent of those horses would fall within a certain range.” But that also means that some healthy horses will be outside the norm. “About 5 percent of horses that are totally normal might be either a little higher or lower,” Wilson says.
When evaluating your horse’s blood results, your veterinarian will take this possibility into consideration. “If just one thing is slightly abnormal on one of the blood tests, and it doesn’t fit with anything else on the bloodwork or with what else the horse is doing, we usually don’t worry about that one,” says Wilson.
But this is also why it’s a good idea to have some routine bloodwork done annually—to record your horse’s normal values. Then, your veterinarian will be better equipped to notice significant changes when he’s ill. “Sometimes it’s not necessarily that the blood value was abnormal; it may be just increasing from the last time we saw it,” Wilson says. “This might still be within the normal range, but it could be a big increase for that horse if he has always been lower.”
At Woodside Equine Clinic in Ashland, Virginia, says Claudia True, DVM, “we offer wellness packages for our clients—they get physical examinations, vaccines, dental checks and fecal egg counts, and they can add a CBC and a blood chemistry. With these we would be looking for underlying abnormalities such as liver and kidney issues.” But some of the results they have seen were surprising:
“It was interesting to see the bell curve on these blood tests, across the board,” True says. “We had a couple of horses with really low white counts. If those were sick horses and you found that number, you’d assume the horse had a viral infection or overwhelming bacterial infection. One of the counts was so low that I was very concerned and talked to our internal medicine specialist about it. I went back a couple weeks later and checked again, and the white count was still fairly low. Apparently this is normal for that horse, even though it was way down on the bell curve for all the horses.”