OGT Reference Provider

Background

The Equine Metabolic Syndrome (EMS) consists in a range of metabolic disorders predisposing horses and ponies for laminitis. The term Insulin dysregulation describes an exacerbated insulin response to oral carbohydrates and may therefore involve incretin signaling. It is one of the central components of EMS alongside with regional or generalized obesity.

Insulin resistance results from an altered response of peripheral tissues to insulin and is associated with insulin dysregulation. It is however not present in every horse suffering from insulin dysregulation. This is why diagnostic tests for EMS should not rely solely on insulin-sensitivity.

Protocol for the Oral Glucose Test (OGT):

  1. Let the horse fast overnight.
  2. Collect a basal blood sample.
  3. Administer 1 g glucose/kg bodyweight in 2L of water via naso-gastric tubing.
  4. Collect a second sample around 120 min (maximal range 90 and 180 min). The horse should not be allowed to eat in the meantime.
  5. Analyze the samples for glucose and insulin. The latter should be measured using the Mercodia® Equine Insulin ELISA to ensure a valid diagnosis based on the here provided reference range.

In contrast to tests like the Combined Glucose/Insulin Test (CGIT), this test has the advantages of being more practical to perform in a field environment and to assess postprandial hyperinsulinaemia under standardized conditions. Furthermore, enteral glucose can activate incretin signaling. The activation of incretin signaling is not achieved by intravenous glucose infusion, this why the OGT is probably better suited to detect insulin dysregulation, while the other tests are more relevant for insulin resistance.

This Webapp is based on a paper which tries to provide a more consistent reference range for insulin during the OGT. Further, by modelling the insulin responses of approximately 30 horses considered healthy during the OGT, it is capable of alleviating the requirements on timing. Actually, drawing the second blood sample exactly 120 min after the tubing might not be achievable under practical settings outside of a hospital. This App provides a dynamic reference range for insulin at any time-point between 90 and 180 minutes. These references are currently only available for insulin measured using the Mercodia® Equine Insulin ELISA. However, we are currently working on further dynamic reference ranges for a broader selection of immunoassays used for quantification of equine insulin as the Mercodia® Equine Insulin ELISA is not widely used yet. If you struggle finding a laboratory using this assay you can contact our partner laboratory.

Check insulin status

Measured insulin was µIU/mL. The sample was drawn min after glucose administration.

More informations

Insulin dysregulation is a central part of the Equine Metabolic Syndrome and can be detected using OGT. However, it might also occur in horses affected by Pars Pituitary Intermedia Deficiency (PPID), formerly known as Equine Cushing Syndrome. This is why horses that where found positive in the OGT and could possibly be affected by PPID (age, other clinical signs) should also be tested (e.g. by TRH stimulation test), and if necessary treated, for this disease.

The management of patients with EMS mostly consists in an optimization of the diet and exercise. Energy intake has to be reduced gradually and adapted to the horse's actual needs, which are sometimes difficult to evaluate for the owner. Exercise is not limited to a more intense training but also includes changes in the stables like access to a paddock, more space for social interaction or putting obstacles in the paddock to make the route from roughage to water circuitous etc. More specific advices and suggestions can be found in literature.

Suggested readings:

For more details about the protocol recommended for use with this reference values please read following paper:
Warnken T, Delarocque J, Schumacher S, Huber K, Feige K. Retrospective analysis of insulin responses to standard dosed oral glucose tests (OGTs) via naso-gastric tubing towards definition of an objective cut-off value. Acta Veterinaria Scandinavica 2018;60. doi:10.1186/s13028-018-0358-8.

The webapp was written by Julien Delarocque upon an original idea from Tobias Warnken. It is provided without any warranty. Hosting is provided by GitHub.