Measuring glycaemic responses: duplicate fasting samples or duplicate measures of one fasting sample?

Area of Science:

• Nutrition science
• Metabolic studies
• Human physiology

Background:

• Accurate measurement of glycaemic response is crucial for understanding metabolic health.
• Incremental area under the curve (AUC) is a key metric for glycaemic response.
• Fasting blood glucose (FBG) is often used to standardize AUC calculations.

Purpose of the Study:

• To investigate if using two fasting blood samples improves the precision of glycaemic response (AUC) measurements.
• To compare the precision of AUC calculated using different FBG estimates.

Main Methods:

• Thirteen healthy subjects consumed four different test meals.
• Two fasting blood samples were collected 5 minutes apart (-5 min and 0 min).
• Glucose levels were measured three times in each sample, and AUC was calculated using various FBG estimates.

Main Results:

• AUC precision was unexpectedly higher when calculated using the mean glucose from the 0-minute sample (FBG0) compared to the average of two fasting samples.
• A 95% confidence interval of +/-29.8 for AUC using FBG0 required 13 subjects, whereas 14 subjects would be needed for the same CI using the average of two samples.

Conclusions:

• Collecting two fasting blood samples does not necessarily enhance, and may decrease, the precision of AUC for glycaemic response.
• Further research is required before mandating two fasting blood samples for glycaemic index determination.