Does a white male with a triglyceride level of 98 mg/dL, high‑density lipoprotein cholesterol of 62 mg/dL, and fasting insulin of 5.2 µU/mL have good insulin sensitivity?

Assessment of Insulin Sensitivity Based on Lipid and Insulin Parameters

This white male demonstrates excellent insulin sensitivity based on his favorable triglyceride-to-HDL ratio and low fasting insulin level.

Interpretation of the Triglyceride-to-HDL Ratio

The triglyceride-to-HDL cholesterol ratio is a validated surrogate marker for insulin resistance in white populations, and this patient's values are highly favorable:

• Calculated TG/HDL ratio: 1.58 (98 mg/dL ÷ 62 mg/dL)
• This falls well below the optimal cut-point of 2.5 for men that identifies insulin resistance 1
• Research demonstrates that TG/HDL ratios >3.5 in men identify insulin-resistant subgroups with significantly higher fasting insulin, blood pressure, BMI, and cardiometabolic risk 1
• In white European populations specifically, the TG/HDL ratio shows strong correlation with insulin resistance (area under ROC curve 0.74-0.75), making it a reliable screening tool 2

The optimal cut-points for detecting insulin resistance range from 0.9-1.7 mmol/L (2.0-3.8 mg/dL) for the TG/HDL ratio, and this patient's value of 1.58 is at the lower end of this range, suggesting good insulin sensitivity 2.

Fasting Insulin Assessment

The fasting insulin of 5.2 µU/mL strongly supports insulin sensitivity:

• This value is substantially below the threshold of 13.13 µU/mL used to define insulin resistance 3
• Research identifies an optimal cut-point of 109 pmol/L (approximately 15 µU/mL) for fasting insulin to detect insulin resistance, with 57% sensitivity and 85% specificity 4
• The patient's fasting insulin is less than half this threshold, indicating robust insulin sensitivity

Clinical Significance of Combined Markers

When both markers are favorable, as in this case, insulin sensitivity is highly likely:

• Studies demonstrate that plasma triglyceride concentration and the TG/HDL ratio are among the most useful metabolic markers for identifying insulin-resistant individuals, with sensitivity of 64-67% and specificity of 68-71% 4
• A weighted combination of fasting insulin and triglycerides provides higher sensitivity while maintaining specificity compared to using fasting insulin alone 5
• This patient's triglycerides (98 mg/dL) are well below the optimal cut-point of 130 mg/dL for identifying insulin resistance 4

Race-Specific Considerations

The interpretation is particularly reliable because the patient is white:

• The TG/HDL ratio performs as an acceptable marker of insulin resistance in whites (AUC 0.77 for men) but is a poor predictor in African Americans (AUC 0.63) 3
• Racial differences exist because African Americans have significantly lower triglycerides and TG/HDL ratios despite comparable or higher insulin levels 3, 6
• Guidelines explicitly state that routine insulin testing is not recommended for most individuals with or at risk for diabetes, as these assays are primarily useful for research purposes 6

Important Caveats

While these markers suggest good insulin sensitivity, recognize their limitations:

• The sensitivity of TG/HDL ratio and fasting insulin to detect insulin resistance is only 40-67%, meaning some insulin-resistant individuals may be missed 1, 4
• The specificity is better at 68-85%, so a favorable result (as in this case) is more reliable for ruling out insulin resistance 1, 4
• Gold standard measurement remains the euglycemic insulin clamp, but this is impractical for clinical use 5