Plasma Glucose Surpasses A1c for Flagging Early Dysglycemia

Miriam E. Tucker

April 28, 2022

Researchers published the study covered in this summary on as a preprint that has not yet been peer reviewed.

Key Takeaways

  • In 15 people with normal A1c levels (< 5.7%; 39 mmol/mol) but at high risk for developing type 2 diabetes both 1-hour interstitial continuous glucose monitoring (CGM) and a 1-hour plasma glucose (PG) measure during an oral glucose tolerance test (OGTT) could identify glycemic variability and dysglycemia, and hence, may be superior to A1c as early indicators of incident dysglycemia.  

  • CGM may be a potential alternative to PG as the best way to assess a patient's responses during an OGTT.

Why This Matters

  • Identifying dysglycemia at an early stage allows for lifestyle intervention to prevent or slow progression to type 2 diabetes.

  • Although A1c is widely used to screen for prediabetes (5.7%-6.4%; 39-46 mmol/mol) and type 2 diabetes (≥ 6.5%, 48 mmol/mol), it is insensitive for identifying the early stages of beta-cell dysfunction.

  • People with incident type 2 diabetes are often diagnosed after significant beta-cell dysfunction has already occurred.

Study Design

  • 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.

Key Results

  • 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.


  • The COVID-19 pandemic restricted recruitment.


  • The study received partial funding from Abbott Diabetes Care.  

  • None of the authors had commercial disclosures.

This is a summary of a preprint research study " Continuous glucose monitoring and 1-hour plasma glucose identifies glycemic variability and dysglycemia in high-risk individuals with HbA1c <5.7% " written by authors primarily based at the New York University Grossman School of Medicine, New York City, on Research Square and provided to you by Medscape. The study has not yet been peer reviewed. The full text of the study can be found on


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