After last weekend's revelation that Kentucky Derby winner Medina Spirit had tested positive for betamethasone post-race, trainer Bob Baffert outlined a few different methods for figuring out how the drug got into the horse's system, including hair testing the horse to look for the presence of the drug. On Tuesday, it seemed the need for investigative work was through, since Baffert admitted the horse had indeed been treated with a topical prescription that contained betamethasone.
Still, his suggestion raised questions about how hair testing can help in cases like that of Medina Spirit. Many have hoped hair testing would be the next great advance in racing's drug testing program, able to detect what blood tests cannot.
Hold your horses, experts say.
Using hair to detect the presence of drugs works because a stand of hair contains melanin, which gives it color and which carries a slight negative ionic charge. That means that when drugs go through a horse's system, those with a slightly positive ionic charge bind to the melanin of the hair at the base where it's growing out from the horse's skin. Laboratories can find the resulting band of the drug in question sitting crossways inside the hair shaft if they have a sample of the hair. Horses with black hair will bind drugs easily; those with less melanin in their hair, like grays and roans, do not retain drug remnants in that hair as readily.
Only the drugs with a slightly positive charge are going to bind to hair well enough to be detected. Dr. Rick Sams, equine drug testing expert and former lab director for HFL Sport Science, said this works well for certain types of drugs.
“Clenbuterol has a negative charge on it, it binds to melanin and it can be detected at a very low level because a lot of it binds to the hair,” said Sams. “Negatively-charged substances like flunixin, like phenylbutazone, are repelled by the negative charge on melanin and do not readily bind to the hair sample even though the blood concentration may be substantially higher than the concentration of substances like clenbuterol.”
Steroids – both anabolics and corticosteroids – are neutral, so they're not attracted to hair. Anabolic steroids are excreted through skin glands and may appear on the outside, rather than the inside, of the hair shaft, but that makes it difficult to say whether a horse was exposed to the steroid externally or internally.
A hair test would probably not detect a corticosteroid like betamethasone in a horse, because it wouldn't bind well to the melanin. If hair testing had been done on Medina Spirit, it wouldn't show the drug but that would be because it couldn't, not because it had never been given.
Then there's the question of gathering that hair sample.
“There are lots of challenges with hair testing that would need to be addressed and standardized,” said Scollay. “For example, I'm terrible at pulling manes, just terrible. I have a hard time with one pull or even two pulls getting a sufficient sample. I'm pulling and pulling and pulling and I finally get what I need. There are some people who just use scissors. If you look at those samples, they're not necessarily even cuts. If you're at the laboratory, you don't know how much hair remained on the neck between the site of the cut and the hair follicle itself.”
Without the root of the hair, Scollay pointed out there's also no way to conduct DNA testing on a sample, should there ever be a question about whether the sample came from the horse in question – and of course, with the majority of Thoroughbreds being bays, the color of the hair isn't going to be much help.
Hair testing also doesn't provide particularly specific information about drug administration, and that's why it's most commonly used to find prohibited substances that are never supposed to be given to horses. Finding a little band of drug in a hair shaft tells the tester that the drug was administered, but not how much was given, how it was given, or exactly when. A three- to four-inch length of hair represents about six months of growth. Most often, laboratories could give a range of time when the drug exposure might have happened but it's usually a range of days or weeks, not hours. Some drugs, like clenbuterol, require multiple exposures of a drug before it will show up in hair. Labs can cut the hair into sections to try to narrow the timeframe a drug was given, but that method isn't always a good one.
“The problem is hair sometimes stops growing before it falls out,” said Sams. “The hair shafts grow at basically the same rate but some of them stop growing, so if you do a sample even in sections, you're going to see a distribution of the drug probably through multiple sections just due to the fact some of those hairs stopped growing. It's an imprecise science.”
A hair test is only useful if enough time has elapsed since the administration of the drug for the hair to grow long enough that it can be taken in a sample. Sams said that in research settings, hair has been sampled using a set of clippers and revealed drug administrations from one or two days before – but that in the field, there's no standardized way to take a sample, and it's unlikely a test barn will be able to successfully cut that close to the skin. Scollay said she wouldn't use a hair sample as a basis to confirm a drug administration more recently than two weeks to a month after administration.
Clenbuterol was recently banned in racing Quarter Horses, and as a result, the American Quarter Horse Association conducts hair testing on horses ahead of major stakes races. There have been cases where a hair test has been negative for clenbuterol but a post-race sample has been positive, resulting in sanctions. Ironically, some of those cases were overturned by courts on appeal because trainers successfully argued that the post-race positive must be a mistake due to the negative pre-race hair test. In reality, Scollay said, it's possible two different labs could use different methodologies on the same horse's hair and come up with different results, neither of which should invalidate a post-race test on blood or urine.
Because of these inconsistencies, both experts agree it will be some time before hair testing becomes the go-to in the United States – if it ever does.
“You have to decide what your purpose is with hair testing; it's not going to replace blood and urine testing. It's not going to do it,” she said. “It's a regulatory tool. It's part of your arsenal, but relying on it solely – unless you're dealing with a prohibited substance – you're going to have a challenging time.”
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