Prediabetes Diagnosis Categorized as Diabetes With 2-Hour Plasma Glucose Test

A vial of blood labeled for glucose testing
A vial of blood labeled for glucose testing
Investigators sought to examine whether individuals with prediabetes, based on A1c and fasting plasma glucose levels, would have a diagnosis of diabetes when using a 2-hour plasma glucose test.

Approximately 7% of patients diagnosed as prediabetic with the A1c and fasting glucose test actually have diabetes as well as greater cardiometabolic risk factors based on 2-hour plasma glucose readings, according to a study published in Diabetes and Vascular Disease Research.

Investigators sought to determine the rate of diabetes among individuals tested with 2-hour plasma glucose in the 2005-2014 National Health and Nutrition Examination Survey. Specifically, researchers wished to know how many of these individuals who were diagnosed with prediabetes using A1c and fasting glucose (n=3644) tests actually had type 2 diabetes based on a 2-hour plasma glucose ≥200 mg/dL.

For patients who were classified as having prediabetes based on A1c and fasting glucose, 6.9% were found to have diabetes based on a 2-hour plasma glucose reading of ≥200 mg/dL. For people ≥65 years of age, approximately 15% of participants had diabetes based on 2-hour readings. Compared with non-Hispanic whites, rates of diabetes were lower among non-Hispanic blacks (7.8% vs 3.0%, respectively; P <.01).

In addition, diabetes rates were higher among women compared with men (9.2% vs 4.9%, respectively; P <.01). There were significant associations between a 2-hour plasma glucose ≥200 mg/dL and albuminuria (adjusted odds ratio [aOR], 2.05; 95% CI, 1.33-3.14), elevated alanine aminotransferase (aOR, 1.78; 95% CI, 1.09-2.91), high triglycerides (aOR, 1.64; 95% CI, 1.10-2.44), hypertension (aOR, 2.06; 95% CI, 1.35-3.14), and low high-density lipoprotein cholesterol (aOR, 1.55; 95% CI, 1.01-2.39).

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The cross-sectional nature of this study limited the investigators’ ability to determine whether diabetes based on 2-hour plasma glucose correlated with the development of specific risk factors for cardiovascular disease.

Overall, this study supports the rationale for performing a 2-hour plasma glucose test for identifying diabetes cases and “has important public health implications considering the benefits of identifying and treating diabetes early during the course of the disease.”


Menke A, Rust KF, Cowie CC. Diabetes based on 2-h plasma glucose among those classified as having prediabetes based on fasting plasma glucose or A1c [published online November 1, 2017]. Diab Vasc Dis Res. doi:10.1177/1479164117739316