Talking to the vet about Karo test


 

Just got a text from my vet, and she would like to do a fasted Karo insulin test… I’m not sure how to respond. Jiji had a Karo test last year and seemed sore afterwards, so it’s not something I’m very comfortable with.
Since Jiji is off grass/fed the ECIR diet, would a normal insulin test (without fasting or Karo) be worthwhile? If that’s what I want instead, what is a polite way to ask?
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-Olivia
May 2021, Bemidji, Minnesota
Jiji's Case History
Photo Album


Sherry Morse
 

Hi Olivia,

Dr. Kellon touched on this in her message to you here: Re: Laminitis (groups.io) as far as your vet did not draw blood, then administer Karo and then draw blood again.  Having only half the test done doesn't really give you any valid information as far as how much did the insulin level change from the administration of Karo.  At this point your best bang for your buck is to get just a baseline non-fasting insulin to see what Jiji's current number is.

IME the way to do that is politely tell the vet that you're comfortable with just the non-fasting insulin test being done and remember that it's your horse and your money being spent and the baseline testing should tell you all you need to know.




 

Insulin is a stimulated hormone so it wouldn't give us any helpful information to do a "baseline" without doing the oral sugar test.  Baseline blood glucose is also vary variable with what they are eating so it is best to do it as a oral sugar test after fasting.  Still should help us know if there is a difference between on grass or off grass if you are keeping her off grass but both levels were normal last year in May.  You can only have to fast her 6 hrs if that helps.  Also I was reading that we need to wait to do the oral sugar test/insulin response until after we do out TRH stim so if you could hold off on the karo syrup until I get there, that would be great.
This is what she said after I asked for the baseline?
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-Olivia
May 2021, Bemidji, Minnesota
Jiji's Case History
Photo Album


Sherry Morse
 

Hi Olivia,

You want to test 'baseline' to see what the normal insulin is on the diet you are currently feeding.  That means having the horse non-fasting when the test is done (you can read more about that here: Fasting Insulin – Lab Ref Ranges | ECIR Group, Inc. (ecirhorse.org)

You might want to send her this link as well: DDT +E – Diagnosis | ECIR Group, Inc. (ecirhorse.org)

And the information from Cornell on the OST test  says there should be 2 collections when using the OST - one prior to the administration of Karo and then 2 samples done after the Karo is administered.  If she's not following those guidelines your bloodwork results will be questionable.

 EQUINE ORAL SUGAR RESPONSE TEST: INSULIN EQUINE ORAL SUGAR RESPONSE TEST: INSULIN INSULIN: The HIGH DOSE OST reference range is < 65 uIU/mL. The baseline reference range (< 20 uIU/mL) assumes the sample was collected after an overnight fast. Normal horses will have insulin levels within the reference ranges. In Equine Metabolic Syndrome (EMS), the concentration of insulin is generally greater than the reference values above. Horses are considered to be hyperinsulinemic if the insulin concentration post-OST is >45 uIU/mL if given 0.15 mL/kg karo syrup or >65 if given 0.45mL/kg karo syrup. Both 60 and 90 minute post samples are recommended. High insulin concentrations may also be caused by pituitary pars intermedia dysfunction (PPID)/equine Cushing’s disease), pregnancy, stress, and illness. When alternate explanations for hyperinsulinemia are considered (e.g., PPID, pain or other sources of stress), a leptin test may aid in the diagnosis of EMS. Leptin is usually elevated in untreated EMS and is less affected by other factors that modulate insulin. Leptin, along with ACTH baseline or TRH response testing is recommended if the elevated insulin level may be due to PPID. *Reference ranges for the post-OST were established by the Equine Endocrinology Group.




Eleanor Kellon, VMD
 

The most important thing you can tell your vet is that your horse was sore after the last Karo test and ask if she can guarantee that will not happen again.  She is right that insulin is a stimulated hormone but if you are feeding a known low S/S diet then how much that is stimulating her insulin is exactly what you want to know.

This is a discussion for another day but lab reference ranges are not "normals". The values we use in the calculator are normals for a hay or grass only diet.
--
Eleanor in PA

www.drkellon.com 
EC Owner 2001


LJ Friedman
 

You know I say that we say whatever’s needed to achieve our goals. Just like sometimes will feed our horses and not tell the vet that we did for an insulin test you can say something like a friends horse died from  a karo test or Something which I witnessed, a horse at my barn swelled up for days and days from the karo  test.and I’m just not gonna do it. I wanna remind you, most equine vets  are not all that,  and don’t know much more than we do regarding insulin and Cushing’s etc. so we do need to advocate to achieve our goals
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LJ Friedman  Nov 2014 Vista,   Northern  San Diego, CA

Jesse( over the rainbow) and majestic ‘s Case History 
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Kirsten Rasmussen
 

Hi Olivia,

My suggestion is to say you understand what she is saying and respect her opinion but you're just not conformable giving your horse Karo Syrup again because of her reaction last year, and that's that.  The reason you are asking for non fasting baseline insulin is not to diagnose your horse with EMS/IR, which is what your vet is proposing, but to see where her insulin is on her normal everyday diet so you can determine how well she is tolerating her diet, or whether you need to find a lower sugar hay or make some more changes.  Since high insulin is the cause of endocrinopathic laminitis you need to know how high insulin is on her everyday diet, not under fasted sugar-challenged conditions. 

--
Kirsten and Shaku (IR + PPID) - 2019
Kitimat, BC, Canada
ECIR Group Moderator
 
Shaku's Case History
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