A new position statement from the International Diabetes Federation advises using a 1-hour 75-g oral glucose tolerance test (OGTT) to improve identification of people at risk of developing type 2 diabetes.
“There are many, many people who may appear ‘normal’ if you use A1c or fasting glucose, but if you do a glucose tolerance test, they may have an abnormality after a glucose load. …The 1-hour plasma glucose has been found to be a more sensitive biomarker for the earlier identification of these high-risk individuals,” lead author Michael Bergman, MD, professor of medicine and population health at New York University Grossman School of Medicine, New York City, told this news organization in an interview.
Dr. Bergman presented the document, written by a 22-member international expert panel, on March 6, 2024, at the annual Advanced Technologies & Treatments for Diabetes meeting. It was simultaneously published in Diabetes Research and Clinical Practice.
This is the International Diabetes Federation’s (IDF’s) proposed screening algorithm for “intermediate hyperglycemia” and type 2 diabetes:
- At-risk high-risk individuals are first screened with a validated questionnaire such as the FINDRISK or the American Diabetes Association’s (ADA’s) risk screening tool.
- People identified as high risk should undergo laboratory screening with a 1-hour 75-g OGTT (although a 2-hour OGTT, fasting glucose, or A1c, as currently recommended by several organizations, is still considered acceptable).
- People with a 1-hour plasma glucose value at or above 155 mg (8.6 mmol/L) are considered to have intermediate hyperglycemia and should be prescribed lifestyle intervention and referred to a diabetes prevention program.
- Those with a 1-hour value greater than or equal to 209 mg/dL (11.6 mmol/L) are considered to have type 2 diabetes and should have a repeat test to confirm the diagnosis, with referral for further evaluation and treatment.
The new guidance is based on increasing evidence that the 1-hour test is a better predictor than other tests, including the 2-hour OGTT, of progression to type 2 diabetes and its associated complications, in a variety of populations. The document cites data showing that a plasma glucose of 155 mg/dl or greater on the 1-hour post-75-g test can identify people with undiagnosed type 2 diabetes or who are at increased risk but who have “normal” glucose tolerance as defined by an A1c < 5.7% (38.8 mmol/mol), a fasting plasma glucose < 100 mg/dL (5.6 mmol/L), or a 2-hour value below 140 mg/dL (7.8 mmol/L).
However, even though a 1-hour test may be more convenient than the traditional 2-hour test, incorporating OGTT into busy clinical practice may still pose logistical problems and may not improve ultimate outcomes, Elizabeth Selvin, PhD, MPH, of the Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, told this news organization. “I worry that emphasizing a burdensome test is not going to improve diabetes screening or diabetes prevention. Doing more 1-hour glucose screening is not going to get more people into diabetes prevention programs.”
When an audience member raised the logistics concern during the session Q&A, Dr. Bergman replied, “It’s no different than recommending colonoscopy or a mammogram. … I tell patients that we want to learn more about what is going on before we make a firm diagnosis. … I’ve done more than a hundred 1-hour glucose tolerance tests and have not seen one patient who refused because of inconvenience. Everything depends on the way we discuss things with patients.”