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HbA1c more sensitive than OGTT for identifying prediabetes

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August 25, 2016

HbA1c and oral glucose tolerance tests used to identify prediabetes yielded conflicting results in both Hispanic and non-Hispanic white populations in New Mexico, study data show.

“Diagnostic tests for prediabetes will often provide different answers depending upon which test is ordered,” Mark R. Burge, MD, professor of medicine, endocrinology and metabolism at the University of New Mexico Health Sciences Center in Albuquerque, told Endocrine Today. “HbA1c appears to provide a more sensitive test for prediabetes in a population heavily enriched in Hispanic individuals.”

Mark Burge
Mark R. Burge

Burge and colleagues analyzed data from 215 adults (96 Hispanic; 79 white; 40 other racial and ethnic groups) at risk for but without diagnosed diabetes living in Albuquerque, New Mexico, to test agreement between HbA1c and OGTT among different racial and ethnic groups.

Based on HbA1c results, 48% of participants were diagnosed with prediabetes.

Among Hispanic participants, 74 had no diabetes based on OGTT and 51 had no diabetes based on HbA1c; OGTT indicated no diabetes in 30 participants who were diagnosed with prediabetes based on HbA1c. Prediabetes was indicated by OGTT in 18 participants and in 45 by HbA1c. Compared with OGTT, HbA1c yielded a sensitivity of 67% and a specificity of 60%.

Among non-Hispanic white participants, 58 had no diabetes based on OGTT and 37 had no diabetes based on HbA1c; OGTT indicated no diabetes in 26 participants who were diagnosed with prediabetes based on HbA1c. Prediabetes was indicated by OGTT in 18 participants and in 40 by HbA1c. Compared with OGTT, HbA1c yielded a sensitivity of 71% and a specificity of 55%.

“Our study shows lack of agreement between the HbA1c and OGTT for glucose homeostasis status among Hispanic and [non-Hispanic white] adults from New Mexico,” the researchers wrote. “Current guidelines leave it to the clinician to use the criteria they choose to diagnose prediabetes and [type 2 diabetes]. While there are limitations to both the OGTT and the HbA1c, studies continue to question how the HbA1c can best be used as a diagnostic test. Given the results of the current study, HbA1c criteria are most effectively employed with a clear understanding of how these results may vary with those obtained by other means. No matter how prediabetes is diagnosed, the importance of early detection and intervention must be emphasized to prevent unnecessary complications.”

According to Burge, clinicians need a true gold standard test for the diagnosis of prediabetes and diabetes that indicates when organ damage due to hyperglycemia is beginning to occur. – by Amber Cox

For more information:

Mark R. Burge, MD, can be reached at

Disclosure: The researchers report no relevant financial disclosures.

itj+ Perspective

Kwame Osei

Kwame Osei

The authors compared the performance between the diagnosis of prediabetes using HbAIc vs. OGTT in Hispanics and non-Hispanic whites. There was a modest diagnostic sensitivity and specificity for both HbA1c and OGTT in both groups. HbA1c correlated significantly and positively with both fasting and 2-hour post-OGTT plasma glucose levels. However, there was no correlation between the diagnosis of prediabetes by HbAIc and OGTT. The current study is consistent with previous findings of predictive values of HbAIc and OGTT for prediabetes in other ethnic populations. However, unlike previous studies, such as Diabetes Prevention Program, the current study had a very small sample size.
Given the epidemic of prediabetes and diabetes, developing a simple, highly predictive diagnostic tool for prediabetes and diabetes for racial/ethnic populations has been the dream for most clinicians and epidemiologists. However, the burden of the recommended two diagnostic values for both HbAIc and OGTT to establish the diagnosis limits the compliance with these tests. In addition, prediabetes is a heterogeneous disorder comprising at least three distinct pathogenic subgroups (IFG, IGT and IFG/IGT). These are determined, in part, by the degree of severity of beta-cell dysfunction and peripheral and hepatic insulin resistance, as well as hepatic glucose production. Furthermore, previous studies have demonstrated that, for comparable plasma glucose levels, HbAIc tends to be higher (0.3% - 0.5%) among African Americans and Hispanics when compared with whites. The mechanism for this HbA1c and glucose dissociation or paradox in ethnic populations remains debatable. These studies suggest that we need a novel, alternate diagnostic tool(s) for screening categories of glucose tolerance for clinical and epidemiological use in various ethnic/racial populations.

Kwame Osei, MD, FACE, FACP
Endocrine Today Editorial Board Member, Professor Emeritus of Medicine and Exercise Physiology, Division of Endocrinology, Diabetes and Metabolism, The Ohio State University Wexner Medical Center

Disclosure: Osei serves on the scientific advisory boards of AstraZeneca, Lilly and for Merck.