Common Blood Test Could Predict Diabetes: Study

A common type of blood test known as the random plasma gluocse (RPG) test may be able to predict which patients will develop type 2 diabetes, according to a new study in the journal PLOS ONE looking at Veterans Affairs (VA) data.


The random plasma glucose test checks glucose levels at any given time, without fasting. A diabetes diagnosis is made at a level of 200 mg/dl along with classic diabetes symptoms, such as frequent urination, intense thirst, blurred vision, unexpected weight loss and extreme fatigue. (The test should be repeated on a second occasion to confirm diagnosis.)

To see whether random plasma glucose levels below the threshold for diabetes could be used to determine which patients would develop the condition, VA researchers looked at data from more than 900,000 patients who were not already diagnosed with the condition. All of the subjects had had at least three random plasma glucose tests throughout the year, most of which were taken in the course of a regular doctor’s appointment not specifically related to diabetes screening.

Over five years of follow-up, about 10% of the group developed type 2 diabetes. The researchers found that plasma glucose levels that were elevated, but not high enough to meet the diagnostic criteria for diabetes, “accurately predicted the development of diabetes within the following five years.” Those who had at least two tests of 115 mg/dl or higher within a year were very likely to receive a diabetes diagnosis within a few years, and those with levels of 130 mg/dl or higher were even more likely.

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The researchers recommend that patients who have two random plasma glucose tests with results at 155 mg/dl or higher receive follow up testing for diabetes, such as a fasting glucose or A1C test.

“Although screening for prediabetes and diabetes could permit earlier detection and treatment, many in the at-risk population do not receive the necessary screening,” says lead author Mary Rhee, MD. “These findings have the potential to impact care in the VA and in the general U.S. population, as random plasma glucose levels — which are convenient, low-cost, and ‘opportunistic’ — could appropriately prompt high-yield, focused diagnostic testing and improve recognition and treatment of prediabetes and early diabetes.”

Want to learn more about diagnosing type 2 diabetes? Read “Diagnostic Tests for Type 2 Diabetes,” “Diabetes Testing: Type 2 Diabetes” and “HbA1c.”

Diane Fennell

Diane Fennell

Senior Digital Editor for, Fennell has 16 years’ experience specializing in diabetes and related health conditions. Based in New York City, she has a degree from Columbia University.

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