HOMA-IR: Homeostatic Model Assessment for Insulin Resistance
HOMA-IR is a validated mathematical model used to estimate insulin resistance from fasting glucose and insulin concentrations, serving as a simple clinical and epidemiological tool that requires only a single plasma sample. 1
Definition and Calculation
HOMA-IR is calculated using the following formula:
- HOMA-IR = [Fasting insulin (μU/mL) × Fasting glucose (mmol/L)] / 22.5 1
This model was originally described in 1985 and has since become widely used in clinical practice and research settings due to its simplicity compared to more invasive methods of measuring insulin resistance 1.
Clinical Applications
HOMA-IR is particularly useful in:
- Epidemiological and cohort studies to assess insulin resistance 1
- Evaluating insulin sensitivity in patients with type 2 diabetes, including those on insulin therapy 2
- Screening for metabolic syndrome risk 3
- Guiding pharmacological treatment decisions, particularly for patients with elevated insulin resistance values 4
Interpretation and Cut-off Values
- Higher HOMA-IR values indicate greater insulin resistance
- Cut-off values may vary across populations and BMI categories 3
- A cut-off of approximately 2.35 has been identified to discriminate metabolic syndrome in some populations 3
- Values tend to increase with higher BMI categories 3
Correlation with Gold Standard Methods
HOMA-IR has been validated against more complex physiological methods:
- It shows good correlation with the euglycemic clamp test (r=-0.753), which is considered the gold standard for measuring insulin resistance 2
- Log-transformed HOMA-IR correlates with various clinical parameters associated with insulin resistance, including BMI, waist circumference, visceral fat area, triglycerides, and HDL-cholesterol 2
Recent Developments
Recent research has explored alternative approaches to calculating HOMA-IR:
- HbA1c-derived estimated average glucose (eAG) can be used as an alternative to fasting glucose in HOMA-IR calculations 5
- This approach may be particularly useful when fasting glucose measurements are difficult to obtain or prone to pre-analytical errors 5
Limitations and Caveats
- HOMA-IR may not accurately detect diet-induced insulin resistance in some cases 6
- Its accuracy may be limited when pancreatic function is compromised 6
- As with all models, the primary input data (insulin and glucose measurements) need to be robust 1
- HOMA-IR should not be used in isolation to measure beta-cell function 1
- More accurate methods (e.g., euglycemic clamp or minimal model analysis) may be needed to detect longitudinal changes in insulin resistance with confidence 6
Clinical Implications
For patients identified with elevated HOMA-IR values:
- Metformin is recommended as the first-line pharmacological treatment, particularly in overweight patients 4
- Lifestyle modifications including diet changes and physical activity are essential components of management 4
- Regular monitoring of glycemic control is recommended, with A1C checked quarterly until targets are achieved 4