Pick an acronym, any acronym. Veterinarians seeking to confirm whether a horse has insulin resistance (IR) have several tests from which to select—generally identified by a lineup of letters—though one particular approach is currently the most common for IR testing. While researchers have evaluated several of the tests for quantifying systemic IR, until recently no one had compared the tests for agreement, or consistency of results.
“We don’t know how these tests compare in the same group of horses,” said Laura Dunbar, DVM, an internal medicine resident at The Ohio State University’s College of Veterinary Medicine, in Columbus, referring to the variety of horse populations in previous research. She and her colleagues evaluated four tests in 12 healthy adult light-breed horses, and she presented their results at the 2015 American College of Veterinary Internal Medicine Forum, held in Indianapolis in June.
At its simplest, IR is a reduction in insulin sensitivity that makes it more difficult for cells to take up blood sugar for metabolism or storage. Insulin resistance is important because aside from being harmful to the horse’s body—the condition is often likened to “pre-diabetes” in humans, a condition that precedes the onset of Type II diabetes—researchers have linked it to the development of laminitis. Dunbar and team compared four common methods of insulin sensitivity testing: basal serum insulin and glucose concentration, the oral sugar test (OST), the combined glucose-insulin test (CGIT), and the insulin-modified frequently sampled intravenous glucose test (FSIGTT). The veterinary community often employs a combination of basal insulin/glucose and the OST—the most practical evaluations.