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Several national and international medical groups issued a consensus statement recommending the adoption of a new glycated hemoglobin (A1C) reference standard—and other changes in how blood glucose levels are reported—at the European Association for the Study of Diabetes (EASD) meeting, held September 18–21 in Amsterdam. The statement, which was simultaneously published in Diabetes Care and Diabetologia, includes the backing of EASD, the American Diabetes Association (ADA), the International Diabetes Federation (IDF), and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).1,2
Following the statement's release, labs worldwide will begin reporting glycated hemoglobin in terms of (1) the familiar A1C percentage, (2) as millimoles per mole (mmol/mol), and (3) a new benchmark, the estimated average glucose (AG), provided in mg/dl (or mmol/l). The developments are intended to clarify technical issues related to how A1C is measured in clinical labs and make the results more useful and meaningful for clinicians and patients (DOC News, May 2007, page 3, and August 2007, page 6).
The new AG measure is meant to help patients interpret the percentage A1C reading by giving them mg/dl averages that correspond with the glucose monitoring scale they use in home blood glucose testing.
RESEARCH SUPPORT FOR AG
At the EASD meeting, a panel of experts released the findings of a study supporting adoption of the AG measure. The study was designed to determine, for the first time, how closely levels of A1C track with long-term levels of blood glucose.
The A1C-Derived Average Glucose (ADAG) study included 643 participants representing a range of A1C levels. Blood glucose values were obtained by continuous blood glucose monitoring and correlated with A1C tests performed in a clinical lab.
Preliminary results from 427 subjects who participated in a first leg of the ADAG study were reported at EASD. Final results of the study are expected in 2008. Thus far, investigators have found a "linear correlation across a wide range of A1C" values, says Robert Heine, MD, PhD, of EASD. Heine is professor of diabetology and director of the Diabetes Centre at VU Medical Center in Amsterdam.
The study upholds AG's accuracy as a clinical standard, says Judith Kuenen, MD, also of VU Medical Center. "We have established a validated relationship between A1C and average glucose across a range of diabetes types and patient populations."
NEW LAB MEASURE
Until now, the results of A1C tests had been calibrated to a reference established by the National Glycohemoglobin Standardization Program (NGSP). A new method devised by IFCC uses mass spectrometry to measure A1C, which is more accurate and precise than methods previously used based on the past work of NGSP and other similar programs.
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The NGSP standard has been mathematically correlated to the new IFCC
reference. "Doctors and patients won't notice anything different"
in how A1C tests are done, says Richard Kahn, PhD, ADA's chief scientific and
medical officer. 
References
2. Consensus statement on the worldwide standardization of the HbA1C
measurement. Diabetes Care 30:2399–2400, 2007.
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| DOC News | Diabetes | Diabetes Care | Clinical Diabetes | Diabetes Spectrum |
