Plasma Glucose Surpasses A1c for Flagging Early Dysglycemia
This was a single-center, prospective study of 15 adults with A1c levels < 5.7% and at least one additional risk factor for type 2 diabetes such as overweight, obesity, hypertension, metabolic syndrome, hypertriglyceridemia, or a first-degree relative with type 2 diabetes, but with no personal history of prediabetes or diabetes. Each participant received a CGM and then 3-7 days later had an overnight fast followed by a 2-hour OGTT with PG measured at baseline and 1 and 2 hours after challenge. Participants continued to use the CGM device for up to 14 days after placement.

The average age of participants was 50 years, 12 (80%) were men, average A1c was 5.3%, and average body mass index was 32.7 kg/m2. Participants were divided into two groups based on their 1-hour PG levels during the OGTT: seven had a low PG of 155 mg/dL (8.6 mmol/L) and eight had a higher level. There were no statistical differences in PG and CGM interstitial glucose levels during the OGTT. A1c levels were similar in the 1-hour high and 1-hour low PG groups. In contrast, mean CGM glucose levels over 12 days (average CGM use duration) were significantly lower in the 1-hour low PG group compared with the 1-hour high PG group. The 1-hour high PG group had higher daily mean glucose levels than the 1-hour low PG group regardless of whether participants wore their CGM for 3 or 12 days. Three different metrics of glycemic variability tracked by the CGM — mean amplitude of glycemic excursions (MAGE), standard deviation (SD), and lability index (LI) — all correlated with 1-h PG regardless of whether participants wore their CGM for 3 or 12 days. MAGE, SD, and LI were significantly higher in the 1-hour high PG group than the 1-hour low PG group, suggesting that 1-hour PG correlates with glycemic variability indices and can be assessed after only 3 days of wearing a CGM.