From the Guidelines
Diagnosis of Insulin Resistance
Insulin resistance is typically diagnosed through a combination of clinical evaluation and laboratory assessments.
- A fasting plasma glucose test is often used as an initial screening tool, with levels between 100 mg/dL (5.6 mmol/L) and 125 mg/dL (6.9 mmol/L) indicating impaired fasting glucose 1.
- An insulin sensitivity test, such as the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), may also be utilized to assess insulin resistance.
- A 2-hour oral glucose tolerance test (OGTT) with measurements of glucose and insulin levels at 0,30,60,90, and 120 minutes can provide additional information on glucose metabolism and insulin sensitivity.
- In certain cases, fasting plasma insulin levels may be measured to assess hyperinsulinemia, with levels above 20 mU/L indicating high insulin resistance 1. It is essential to note that medications such as metformin may be used to assess insulin sensitivity, but this is not a primary diagnostic tool. Clinical evaluation should also include an assessment of risk factors, such as obesity, family history of type 2 diabetes, and signs of insulin resistance, to guide the diagnostic process 1.
From the Research
Diagnostic Methods for Insulin Resistance
The diagnosis of insulin resistance can be achieved through various methods, each with its advantages and disadvantages. Some of the most commonly used methods include:
- Hyperinsulinemic-euglycemic clamp, which is considered the most precise test but is primarily used in research due to its complexity and intrusiveness 2, 3, 4, 5
- Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI), which are based on measuring fasting glucose and insulin levels and are widely used in clinical settings 2, 3, 4, 5, 6
- Oral Glucose Tolerance Test (OGTT), insulin tolerance test, and the Matsuda Index, which provide additional information on insulin sensitivity 2, 3, 4, 5
- Insulin suppression test and minimal model analysis, which are used in specific clinical circumstances 2, 4
Advantages and Limitations of Diagnostic Methods
Each diagnostic method has its advantages and limitations. For example:
- The hyperinsulinemic-euglycemic clamp is considered the gold standard but is complex and expensive 3, 4, 5
- HOMA-IR and QUICKI are simple and widely used but may have poor precision 3, 4, 5
- OGTT and insulin tolerance test provide additional information but may be time-consuming and require multiple measurements 2, 3, 4
Clinical Applications of Diagnostic Methods
The choice of diagnostic method depends on the clinical context and the purpose of the assessment. For example:
- HOMA-IR and QUICKI are suitable for clinical use, while other indices such as HES, McAuley, Belfiore, Cederholm, Avignon, and Stumvoll index are suitable for epidemiological or research purposes 5
- HOMA-IR can be used to evaluate insulin sensitivity in patients with type 2 diabetes on insulin therapy, as shown in a study that correlated HOMA-IR with insulin resistance index assessed by the clamp test 6