Serum Amyloid A: A Stall Side Horse Blood Test For Infection

Last Friday night, my horse, Rex, got very sick.  We all dread making the Friday night phone call to our vet, but in this case, it was absolutely necessary.
 
A few days earlier, Rex had broken out in hives.  There wasn't one square inch of him that did not have hives.  It had been many years since he last had hives, but "dex" (dexamethasone, a prescription corticosteroid) usually took care of it in 2 or 3 days.  It was now day 3, and he still had massive hives.  He also had bug bites on his tummy and in between his front and back legs, (probably from culicoides), which I had been battling for the past 2 weeks. 

I took him up to the barn to cold hose him.  I put my hand on the inside of his hing leg, and his skin felt like it was on fire.  He did not want to be touched, and I completely understood why.  Then I took his temperature and discovered he had a fever.  It was almost 3 degrees above what is normal for him.
 
As an aside, I believe every horse owner should know their horse's vital signs including temperature. Generally speaking, a horse's temperature range is between 99 and 101. It's important to know what's normal for your horse so you can determine the severity of a fever.  Here's a link to My Helpful Links page where you can download a free chart I put together many years ago summarizing how to check your horse's vitals.
 
Ok....Back to the Rex story....
At that point, I called my vet.  She said she would be there as soon as she finished up her current call.  When she arrived approximately 90 minutes later, she asked detailed questions about the current situation and took Rex's vitals. His temperature had gone up another whole degree in 90 minutes.  Quite frankly, Rex looked miserable.
 
After discussing various options, we decided to give Rex a Serum Amyloid A test.
 
Do You Know What a Serum Amyloid A (SAA) Test Is?
 
Give Me the Short Story....
SAA is a biomarker protein produced in the liver and secreted into the bloodstream when there is inflammation caused by an infection, trauma etc.  In a normal healthy horse, SAA is found in very very low quantities and is not secreted until inflammation occurs.  The normal SAA range is below 20 mg/L.  (milligrams per liter)  New devices enable your vet to test your horse's blood for the presence of SAA stall-side and get the results in about 8-10 minutes.  This is in contrast to sending blood off to the lab to be tested for other infection markers that can take longer to show up.  Research is ongoing to determine if and when SAA testing will supplant some forms of more traditional blood testing and when each is appropriate.

A Picture is Worth a Thousand Words....
SAA Production and Response (image by Tridelta Development Ltd)

Reference 1:  Tridelta Development Ltd website

Give Me The SAA Geeky (but not too geeky) Details....

SAA is a member of a group of proteins called Acute Phase Proteins which are thought to be part of the body’s basic first line defense against infection, disease or trauma. In response to a challenge by, for example an infection, the body sends chemical messengers to the liver which then produces and releases SAA into the bloodstream to help fight off the challenge.¹  Researchers have discovered that when there is an infection or challenge to the immune system, SAA levels begin to rise almost immediately... and they can rise to levels hundreds of times above normal.  SAA is extremely sensitive to the onset, duration, and end of the disease process. 
​
The SAA test is a simple blood test performed stall-side with a reader that is about the size of a smartphone.  The device is pictured above.  It takes about 8-10 minutes to get the results.  That means your vet will have additional valuable information about what is going on in your horse's body very quickly and can start treatment immediately.  SAA is normally present only in very low levels. As mentioned above, in a healthy horse, the normal range of SAA is below 20 mg/L (milligrams per liter.)  In response to a challenge, however, SAA is produced in very high levels often 600, 800 or even 1000 mg/L.
 
So, What Were the Results of Rex's SAA Test?
2150!!  (Yes, I did say below 20 was normal.)  In case you're wondering, I'm not missing a decimal place in the 2150. It was two thousand one hundred and fifty.  Needless to say, we started treatment immediately!  By the following morning, Rex had improved greatly.  I am happy to report that 10 days later, Rex is feeling almost 100%.  Phew!!

The Bottom Line.....
There is still much to be learned about SAA and its potential uses in identifying various diseases and medical conditions much earlier than was previously possible. Research is ongoing to determine if and when SAA testing (in horses, humans and other animals) will supplant some forms of more traditional blood testing and when each is appropriate.

• Here's a link to a great SAA Q&A in TheHorse.com
  
• You can also Google Serum Amyloid A and/or speak to your vet if you want to learn more.

Has your horse had an SAA test?  What happened?  Share your story below or on our Holistic Horse Bodyworks Facebook page.

Since this blog is personal, I want to say a BIG thank you to my vet for coming out on a Friday night and to my two good friends and barnmates who stayed with Rex and I and provided excellent support!  I also want to thank the barn owner and the barn manager who helped me care for Rex and were my eyes and ears in between my multiple visits per day taking his temperature and monitoring him.  I owe all of you big time!  It truly takes a village!!