The assessment of insulin resistance in man.

Insulin resistance exists when a normal concentration of insulin produces a less than normal biological response. The ability to measure insulin resistance is important in order to understand the aetiopathology of Type 2 diabetes, to examine the epidemiology and to assess the effects of intervention. We assess and compare methods of measurement and have undertaken a literature review from 1966 to 2001. Quantitative estimates of insulin resistance can be obtained using model assessments, clamps or insulin infusion sensitivity tests. There is considerable variation in the complexity and labour intensity of the various methods. The most well-established methods are the euglycaemic clamp, minimal model assessment and homeostatic model assessment (HOMA). No single test is appropriate under all circumstances. There are a number of well-established tests used to measure insulin resistance: the choice of method depends on the size and type of study to be undertaken. Although the so-called 'gold-standard' test, the euglycaemic clamp, is useful for intensive physiological studies on small numbers of subjects, a simpler tool such as HOMA is more appropriate for large epidemiological studies. It is important to be aware that most techniques measure stimulated insulin resistance whereas HOMA gives an estimate of basal insulin resistance. Caution should be exercised when making comparisons between studies due to variations in infusion protocols, sampling procedures and hormone assays used in different studies.