Table 1.

Insulin sensitivity and β-cell function indices derived from fasting and OGTT measurements of glucose and insulin.

Index	Formula/equation and interpretation
HOMA-IR	Fasting glucose (mg/dL) x fasting insulin (µIU/mL)/405. It can be used as an index representing insulin resistance and β-cell function. The mean 80th percentile in Italian population, considered as cut-off value for insulin resistance, is 2.77 (31).
QUICKI	1/log insulin + log glycemia in mg/dL.The quantitative insulin sensitivity check index (QUICKI) is an empirically derived mathematical transformation of fasting blood glucose and plasma insulin concentrations that provides a reliable, reproducible, and accurate index of insulin sensitivity. The 75th percentile in non-Italian population 0.35 (range 0.34–0.37) (32).
OGIS (0-120 min.)	This method is expressed in ml per minute per square meter of body surface area (ml.min −1 . m − 2). Oral Glucose Insulin sensitivity (OGIS) is comparable to the calculation of glucose clearance obtained in the clamp (32). The mean normal value in non-Italian population is 424. In subjects with GD vary from 323 to 375 (33).
IGI	[Δ insulin (30–0 minutes) (μIU/mL)/Δ glucose (30–0 minutes) (mg/dL)] . Insulinogenic Index (IGI) is used to estimate insulin secretion and is calculated as the change in insulin divided by the change in glucose from 0 to 30 minutes (28,29).
oDI	IGI x 1/Fasting Insulin. Oral Disposition index (oDI) is expressed by calculating the product of insulin secretory capacity and insulin sensitivity. In healthy subjects, the product of insulin sensitivity and insulin secretion is constant (29).

Abbreviations: OGTT, Oral Glucose Tolerance Test; GD, Glucose Dysregulation.