How can we measure insulin sensitivity/resistance?

Insulin resistance represents a major public health problem, as it plays a major role in the pathophysiology of type 2 diabetes mellitus; it is also associated with increased cardiovascular risk and atherogenic dyslipidaemia, and is a central component of the cluster of metabolic abnormalities that comprise the metabolic syndrome. Thus, the development of tools to quantify insulin sensitivity/resistance has been the main objective of a number of studies. Insulin resistance can be estimated with the use of several biological measurements that evaluate different aspects of this complex situation. To that end, it requires various resources, ranging from just a single fasting blood sample for simple indices, such as the HOMA or QUICKI, to a research setting in which to perform the gold-standard hyperinsulinaemic-euglycaemic clamp test. The choice of method for evaluating insulin resistance depends on the nature of the information required (classification of individual subjects, group comparisons, precise measurement of either global, muscle or liver insulin sensitivity/resistance) and on the available resources. The aim of this review is to analyze the most frequently used assay methods in an attempt to evaluate when and why these methods may be useful.