From the Guidelines
The HOMA calculation uses fasting total insulin, not free or random insulin, as it is the standard measurement used in clinical practice and laboratory testing. This is based on the evidence from the Journal of Hepatology study 1, which discusses the use of HOMA-IR as a surrogate for insulin resistance in non-diabetic persons. The study mentions that the product of fasting glucose and insulin, divided by 22.5, can serve as a surrogate for insulin resistance, but it does not specify the type of insulin measurement used. However, in clinical practice, total insulin is the standard measurement used, which includes both bound and unbound insulin in the bloodstream.
For proper HOMA calculation, patients need to be fasting for at least 8 hours before blood collection, as the model was developed using fasting values to assess insulin resistance and beta-cell function. Random insulin levels would not be appropriate as they fluctuate significantly based on recent food intake and would not provide a reliable baseline for the mathematical model. The HOMA formula multiplies fasting glucose (in mmol/L) by fasting total insulin (in μU/mL) and divides by a constant to estimate insulin resistance (HOMA-IR) or beta-cell function (HOMA-β), as mentioned in the study 1.
Some key points to consider when using the HOMA calculation include:
- The validity of HOMA-IR depends on the ability of insulin secretion to adapt to insulin resistance, questioning its suitability in overt diabetes, as noted in the study 1.
- The assays for insulin measurements vary widely, and there is no agreement on a threshold defining insulin resistance using HOMA-IR, highlighting the need for standardized insulin measurements.
- Liver disease progression has been associated with persistence or worsening of metabolic abnormalities, including HOMA-IR, emphasizing the importance of accurate insulin resistance assessment.
From the Research
HOMA Calculation
The HOMA (Homeostasis Model Assessment) calculation is a method used to assess insulin resistance and beta-cell function.
- The calculation of HOMA-IR (insulin resistance) and HOMA-B (beta-cell function) is based on fasting glucose and insulin levels 2, 3.
- However, some studies have explored the use of alternative markers, such as C-peptide 4 and glycated hemoglobin (HbA1c) 5, in the HOMA calculation.
Insulin Used in HOMA Calculation
- The original HOMA model uses fasting insulin levels in its calculation 2, 3.
- There is no mention of using free random or total insulin in the provided studies.
- However, one study used C-peptide as a substitute for insulin in the HOMA calculation, suggesting that alternative markers can be used in certain situations 4.