Table 1.

The meaning and equation of each fasting state measure and OGTT-denved index

Index	Definition/Clinical significance	Equation	Reference
Measures of insulin sensitivity
Stumvoll metabolic clearance rate	Correlates with the metabolic clearance rate (MCR) derived from the hyperinsulinemic euglycemic clamp which measures the rate of glucose uptake into tissues (primarily muscle and adipose tissue). MCR from clamp studies is calculated as the average glucose infusion rate divided by the average plasma glucose concentration during the last hour of a hyperinsulinemic euglycemic clamp. Higher levels indicate greater insulin sensitivity.	18.8 − 0.271×BMI − 0.0052×I120 − 0.27×G90	14
Stumvoll insulin sensitivity index	Correlates with the insulin sensitivity index (ISI) derived from the hyperinsulinemic euglycemic clamp and represents the amount of glucose metabolized per unit of plasma insulin. ISI from clamp studies is calculated as the metabolic clearance rate divided by the mean insulin concentration during the same period of the clamp. Higher levels indicate greater insulin sensitivity.	0.226 − 0.0032×BMI − 0.0000645×I120 − 0.0037×G90	14
Matsuda index	Correlates with the rate of whole-body glucose uptake into tissues (primarily muscle and adipose tissue) during the hyperinsulinemic euglycemic clamp. Higher levels indicate greater insulin sensitivity.	$10000∕\sqrt{{\mathrm{G}}_0\times {\mathrm{I}}_0\times {\mathrm{G}}_{\text{mean}}\times {\mathrm{I}}_{\text{mean}}}$ (glucose in “mg/dL” and insulin in “μU/mL”)	15
Measures of β-cell function
Stumvoll insulin secretion, phase 1	Correlates with first phase insulin secretion (rise in insulin levels during the 10 minutes immediately after starting the glucose infusion which rapidly raises glucose levels) during a hyperglycemic clamp. Higher levels indicate greater insulin secretion capacity.	1283 + 1.829×I30 − 138.7×G30 + 3.772×I0	14
Stumvoll insulin secretion, phase 2	Correlates with second phase insulin secretion, the steady state insulin levels during the last hour of the hyperglycemic clamp. Higher levels indicate greater insulin secretion capacity.	287 + 0.4164×I30 − 26.07×G30 + 0.9226×I0	14
Insulinogenic index	Measure of early-phase insulin secretion. For a given rise in plasma glucose during the first 30 minutes of an OGTT, a larger index indicates greater insulin secretion	(I30 − I0)/(G30 − G0)	16
Fasting-state measures
HOMA-IR	Insulin resistance index calculated from fasting glucose and insulin based on a physiologic model of the glucose and insulin relationship in vivo (Homeostasis Model). Lower levels indicate greater insulin sensitivity.	(G0 × I0)/22.5. (insulin in μU/mL)	17
HOMA-%β	Beta-cell function index calculated from the Homeostasis Model. It is expressed as a percent of normal β cell function.	(20 × I0)/(G0 − 3.5) %.	17

Notes: G₀, fasting glucose; G₃₀/G₉₀, glucose 30 and 90 min after the administration of 75g glucose; G_mean, mean glucose during oral glucose tolerance test (OGTT); I₀, fasting insulin; I₃₀/I₁₂₀, insulin 30 and 120 min after the administration of 75g glucose; I_mean, mean insulin during OGTT. Body mass index (BMI) in kg/m², Insulin in pmol/L and glucose in mmol/L unless stated otherwise.