While A1C is well established as an important risk marker for diabetes complications, with the increasing use of continuous glucose monitoring (CGM) to help facilitate safe and effective diabetes management, it is important to understand how CGM metrics, such as mean glucose, and A1C correlate. Estimated A1C (eA1C) is a measure converting the mean glucose from CGM or self-monitored blood glucose readings, using a formula derived from glucose readings from a population of individuals, into an estimate of a simultaneously measured laboratory A1C. Many patients and clinicians find the eA1C to be a helpful educational tool, but others are often confused or even frustrated if the eA1C and laboratory-measured A1C do not agree. In the U.S., the Food and Drug Administration determined that the nomenclature of eA1C needed to change. This led the authors to work toward a multipart solution to facilitate the retention of such a metric, which includes renaming the eA1C the glucose management indicator (GMI) and generating a new formula for converting CGM-derived mean glucose to GMI based on recent clinical trials using the most accurate CGM systems available. The final aspect of ensuring a smooth transition from the old eA1C to the new GMI is providing new CGM analyses and explanations to further understand how to interpret GMI and use it most effectively in clinical practice. This Perspective will address why a new name for eA1C was needed, why GMI was selected as the new name, how GMI is calculated, and how to understand and explain GMI if one chooses to use GMI as a tool in diabetes education or management.

Background: Multiple laboratory tests are used in the diagnosis and management of patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially. Approach: An expert committee drafted evidence-based recommendations for the use of laboratory analysis in patients with diabetes. An external panel of experts reviewed a draft of the guidelines, which were modified in response to the reviewers’ suggestions. A revised draft was posted on the Internet and was presented at the AACC Annual Meeting in July, 2000. The recommendations were modified again in response to oral and written comments. The guidelines were reviewed by the Professional Practice Committee of the American Diabetes Association. Content: Measurement of plasma glucose remains the sole diagnostic criterion for diabetes. Monitoring of glycemic control is performed by the patients, who measure their own plasma or blood glucose with meters, and by laboratory analysis of glycated hemoglobin. The potential roles of noninvasive glucose monitoring, genetic testing, autoantibodies, microalbumin, proinsulin, C-peptide, and other analytes are addressed. Summary: The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are of minimal clinical value at the present time, and measurement of them is not recommended.

OBJECTIVE—Recent studies have confirmed that improved glycemic control decreases the risk of diabetic complications in type 1 and type 2 diabetic patients. The Minimed glucose sensor allows continuous 72-h glucose monitoring and represents a potentially important tool to improve diabetes management. Its use is currently limited to the health care team. Our aim was to evaluate the reproducibility of data provided by the device by comparing data provided by two sensors worn simultaneously by the same subject.

The endothelial nitric-oxide synthase (eNOS) is a key determinant of vascular homeostasis. Like all known nitric-oxide synthases, eNOS enzyme activity is dependent on Ca²⁺-calmodulin. eNOS is dynamically targeted to specialized cell surface signal-transducing domains termed plasmalemmal caveolae and interacts with caveolin, an integral membrane protein that comprises a key structural component of caveolae. We have previously reported that the association between eNOS and caveolin is quantitative and tissue-specific (Feron, O., Belhassen, L., Kobzick, L., Smith, T. W., Kelly, R. A., and Michel, T. (1996) J. Biol. Chem.271, 22810–22814). We now report that in endothelial cells the interaction between eNOS and caveolin is importantly regulated by Ca²⁺-calmodulin. Addition of calmodulin disrupts the heteromeric complex formed between eNOS and caveolin in a Ca²⁺-dependent fashion. In addition, overexpression of caveolin markedly attenuates eNOS enzyme activity, but this inhibition is reversed by purified calmodulin. Caveolin overexpression does not affect the activity of the other NOS isoforms, suggesting eNOS-specific inhibition of NO synthase by caveolin. We propose a model of reciprocal regulation of eNOS in endothelial cells wherein the inhibitory eNOS-caveolin complex is disrupted by binding of Ca²⁺-calmodulin to eNOS, leading to enzyme activation. These findings may have broad implications for the regulation of Ca²⁺-dependent signal transduction in plasmalemmal caveolae.

Trends in the prevalence and control of diabetes defined by hemoglobin A_1c (HbA_1c) levels are important for health care policy and planning. To update trends in the prevalence of diabetes, prediabetes, and glycemic control. Cross-sectional. NHANES (National Health and Nutrition Examination Survey) in 1988–1994 and 1999–2010. Adults aged 20 years or older. We used calibrated HbA_1c levels to define undiagnosed diabetes (≥6.5%); prediabetes (5.7% to 6.4%); and, among persons with diagnosed diabetes, glycemic control (<7.0% or <8.0%). Trends in HbA_1c categories were compared with fasting glucose levels (≥7.0 mmol/L [≥126 mg/dL] and 5.6 to 6.9 mmol/L [100 to 125 mg/dL]). In 2010, approximately 21 million U.S. adults aged 20 years or older had total confirmed diabetes (self-reported diabetes or diagnostic levels for both fasting glucose and calibrated HbA_1c). During 2 decades, the prevalence of total confirmed diabetes increased, but the prevalence of undiagnosed diabetes remained fairly stable, reducing the proportion of total diabetes cases that are undiagnosed to 11% in 2005–2010. The prevalence of prediabetes was lower when defined by calibrated HbA_1c levels than when defined by fasting glucose levels but has increased from 5.8% in 1988–1994 to 12.4% in 2005–2010 when defined by HbA_1c levels. Glycemic control improved overall, but total diabetes prevalence was greater and diabetes was less controlled among non-Hispanic blacks and Mexican Americans compared with non-Hispanic whites. Cross-sectional design. Over the past 2 decades, the prevalence of total diabetes has increased substantially. However, the proportion of undiagnosed diabetes cases decreased, suggesting improvements in screening and diagnosis. Among the growing number of persons with diagnosed diabetes, glycemic control improved but remains a challenge, particularly among non-Hispanic blacks and Mexican Americans. National Institutes of Health.