Insulin resistance is an important issue in public health due to its increasing prevalence among nondiabetic adults and because it often precedes the development of metabolic diseases like type 2 diabetes, which, once present, increases the risk for other diseases, including cancers. Insulin resistance is thought to have an inflammatory component.
There are lots of ways to measure insulin resistance. The gold standard is the euglycemic hyperinsulinemic clamp. In this technique, insulin is infused into a vein to reach a constant level in the blood. Since insulin is being pumped into the blood, the person has artificially high insulin, or hyperinsulinemia. Simultaneously, glucose is also infused at a varying rate until the blood glucose level stabilizes at a normal level. When a person’s blood glucose is normal, this is called eugylcemia (the Greek root “eu-” means “good”). At this point, the rate of glucose infusion exactly equals the amount being taken up by the body’s tissues, which is a direct measure of insulin sensitivity. The more glucose that has to be infused to keep euglycemic, the more’s being taken up, meaning the tissue is more sensitive to insulin.
The problem with this technique is it takes a couple of hours and is relatively expensive. Thus, estimates of insulin resistance that are cheaper and easier to measured have been developed. Two major ones are HOMA-IR and QUICKI. Both just require a single blood draw where fasting glucose and C-peptide (a byproduct of insulin synthesis) are measured. These values are then plugged into an equation that estimates insulin sensitivity. However, these estimations aren’t perfect.