Recommendation Based on Emerging Evidence
“Intermediate hyperglycemia” is the World Health Organization’s term to refer to either impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). These conditions are often called “prediabetes,” especially in the United States, but that term has been controversial because not everyone with IFG and IGT will go on to develop type 2 diabetes, said Dr. Bergman, who is also director of the NYU Langone Diabetes Prevention Program.
“With ‘prediabetes’ you’re labeling someone with a disease they may not develop. It’s not normal, but it’s not diabetes, so it’s an intermediate state,” he explained.
The statement provides a detailed summary of the data from 19 studies supporting use of a 1-hour plasma glucose of ≥ 155 mg/dL (8.6 mmol/L) to diagnose intermediate hyperglycemia and type 2 diabetes, including links between that level of glycemia and worsened metabolic and atherogenic profiles, risk for microvascular and macrovascular complications and mortality, and identification of risks for obstructive sleep apnea, cystic fibrosis-related diabetes mellitus, fatty liver disease, and premature mortality.
One major problem with current testing, Dr. Bergman said, is that “there is a huge disconnect between A1c and glucose values. … Only about 30% of individuals with an abnormal A1c will have an abnormal fasting glucose, and the inverse is also true. There’s a big mismatch between the two.”
Current guidelines suggest using both A1c and fasting glucose, but Dr. Bergman said that even then “you’re still missing about 20-30% who have IGT. … Part of the problem is that the criteria we use for defining abnormal fasting and 2-hour levels are too high. … 140 [mg/dL] for the 2-hour is too high and 100 [mg/dL] fasting is too high. … And that’s one of the reasons why many people progress to type 2 diabetes, because we’re using screening thresholds that are nonphysiologic.”
But Dr. Selvin disagrees, pointing to her own work showing that “using a combination of fasting glucose and A1c for screening does an excellent job at identifying high-risk individuals.”
She’s also unconvinced by other data cited in the paper. “I am deeply skeptical about 1-hour glucose being more prognostic than all other glycemic tests. … Associations of glucose tests with incident diabetes are inherently a circular analysis since diabetes is defined by elevations in those same tests. It is helpful to look at progression of diabetes, but these analyses are not simple and doing them well, especially with head-to-head comparisons against different glycemic tests, is hard,” she said.
In her view, “lifestyle interventions and weight loss should be recommended in at-risk individuals, including those with overweight and obesity, hypertension, metabolic syndrome, etc., regardless of 1-hour glucose test results.”
She added, “If we want to prevent diabetes, we need to focus on preventing weight gain and obesity and managing cardiometabolic risk factors. Lifestyle interventions are not effective unless they are intensive and patients are highly adherent. We need to make lifestyle interventions available and affordable for patients. That is the big barrier. I don’t think more screening with 1-hour glucose is going to help.”
Dr. Bergman pointed out that the International Diabetes Federation represents more than 100 countries, including many that are middle- and low-income. “They need a simple, cost-effective tool for screening effectively. A1c is more expensive, and fasting glucose alone will underestimate disease prevalence. So, the IDF felt, after doing a fairly comprehensive due diligence, that the data warranted recommendation of the 1-hour glucose.”
He’s hoping other organizations like the ADA and the World Health Organization will sign on to bring this guidance into the primary care arena. This news organization reached out to ADA for comment, but their representative hadn’t responded by press time.
Dr. Bergman had no disclosures. Dr. Selvin was supported by the National Institutes of Health.
A version of this article appeared on Medscape.com.