A high normal A1c (HbA1c) reading might be a better, cheaper, and easier-to-use screening tool for prediabetes and diabetes than the laboratory-based oral glucose tolerance test (OGTT).
Presenter and solo investigator Peter Baginsky, MD, associate professor, Touro University College of Osteopathic Medicine, and a diabetes specialist in clinical practice in Santa Rosa, California, United States, presented his findings.
"The most important finding here is that what we would have called a normal A1c, but in the high normal range, is a very valuable way to identifying people who have prediabetes, or diabetes that might otherwise be missed for several years while they are developing complications of diabetes," he said.
As background to the presentation, Dr. Baginsky wrote, "Individuals with prediabetes have substantial risk of developing diabetes (DM) and cardiovascular disease. Moreover, DM can be delayed or prevented in many of these individuals with medications and/or lifestyle changes. Yet many of those at high risk are never screened for prediabetes, often as a result of socioeconomic barriers. A simple and inexpensive screening tool is in great need."
He recruited 73 subjects from medically underserved Latino communities in Northern California. Subjects ranged in age from 19 to 67 years, and 91.8% of them had body mass index > 25.
After overnight fasting, each subject received a standard 75-gram OGTT and was tested for HbA1c.
Results showed that 12.3% of subjects had abnormal glucose levels on OGTT, 5.5% had previously undiagnosed diabetes mellitus, and 6.8% had impaired fasting glucose and/or impaired glucose tolerance.
Dr. Baginsky noted that, as a method of screening for prediabetes or diabetes, HbA1c levels greater than 5.8% had sensitivity of 89%, specificity of 92%, positive predictive value 62%, and negative predictive value 81%.
"This appears to be an extremely useful screening tool," Dr. Baginsky wrote in the conclusion. "Using portable kits, HbA1c could be used to screen large groups of people without access to a laboratory, and identify individuals with prediabetes, who may be candidates for further screening. Thus, the high normal HbA1c may offer significant advantages for this population over a laboratory-based OGTT. A larger-scale study of this test should be performed, to confirm its validity."
Presented at the 66th ADA Scientific Sessions June 2006 [Presentation title: High Normal HbA1c as a Screen for Diabetes and Prediabetes in an Underserved Latino Population. Abstract 1139-P]
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