Testing for insulin dysregulation

Horses with Equine Metabolic Syndrome (EMS) are susceptible to laminitis associated with insulin dysregulation (ID). Advanced cases have markedly elevated resting insulin levels (Basal Insulin Concentration: BIC), and the diagnosis is straightforward. It is quick and easy to carry out a basal insulin test, only requiring a single blood sample. 

Unfortunately, it may not detect many early cases of ID which can have resting insulin levels within the normal reference range.

This may lead owners to conclude that changes to diet and management are not required.

There is a need for a simple test that can be used by ambulatory veterinarians at the owners’ premises to identify more of those suspect cases of EMS that are missed by the BIC test.

Researchers in the Netherlands investigated to see if using an Oral Sugar Test (OST) would be more useful than BIC for detecting ID.

Linda Van Den Wollenberg and colleagues, studied 90 adult horses, of various breeds, used for recreational purposes, and maintained at the owners’ premises in the Netherlands and Belgium. Their work is published in the Journal of Equine Veterinary Science.

The researchers collected blood samples before and 75 minutes after administering sugar solution (0.45g/kg of commercially available corn syrup.)

They compared the number of horses classified as "ID-positive", "ID-suspect", and "ID–not diagnosed" according to the basal insulin concentration (BIC) (>50mU/L; 20-50mu/L and

There was a significant difference in outcome of the results of the two tests. 

The oral sugar test proved to be more useful than the basal insulin concentration. BIC classified 3 horses as ID-positive and 6 horses as ID-suspect (a total of 9/90, 10%). In contrast, the OST classified 25 of the 90 horses (28%) as ID-positive. 

The researchers conclude that, under field conditions, the OST is preferred over the BIC for use as a screening test for ID.

They add that “In addition, our results support the assumption that obese horses and “easy keeper” breeds have a higher tendency of having ID.” They suggest: “further studies are required to assess the repeatability of the OST as we performed it, under different circumstances and within an individual.”

For more details, see:

Comparison of Two Diagnostic Methods to Detect Insulin Dysregulation in Horses Under Field Conditions.

Linda Van Den Wollenberg, Veerle Vandendriessche, Kees van Maanen, Guillaume H.M.Counotte

Journal of Equine Veterinary Science (2020) Vol 88, 102954

https://doi.org/10.1016/j.jevs.2020.102954