The American Diabetes Association (ADA) and the American Association for Clinical Chemistry have determined that the correlation ( r 0.92) in the ADAG trial is strong enough to justify reporting both the A1C result and the estimated average glucose (eAG) result when a clinician orders the A1C test.Members of the ADA Professional Practice Committee, a multidisciplinary expert committee ( ), are responsible for updating the Standards of Care annually, or more frequently as warranted.
Hb Aic 6.6 Trial Is StrongFor a detailed description of ADA standards, statements, and reports, as well as the evidence-grading system for ADAs clinical practice recommendations, please refer to the Standards of Care Introduction ( ). Readers who wish to comment on the Standards of Care are invited to do so at professional.diabetes.orgSOC. ASSESSMENT OF GLYCEMIC CONTROL Glycemic management is primarily assessed with the A1C test, which was the measure studied in clinical trials demonstrating the benefits of improved glycemic control. Patient self-monitoring of blood glucose (SMBG) may help with self-management and medication adjustment, particularly in individuals taking insulin. Continuous glucose monitoring (CGM) also has an important role in assessing the effectiveness and safety of treatment in many patients with type 1 diabetes, and limited data suggest it may also be helpful in selected patients with type 2 diabetes, such as those on intensive insulin regimens ( 1 ). A1C Testing Recommendations Perform the A1C test at least two times a year in patients who are meeting treatment goals (and who have stable glycemic control). E Perform the A1C test quarterly in patients whose therapy has changed or who are not meeting glycemic goals. E Point-of-care testing for A1C provides the opportunity for more timely treatment changes. Thus, A1C testing should be performed routinely in all patients with diabetesat initial assessment and as part of continuing care. Measurement approximately every 3 months determines whether patients glycemic targets have been reached and maintained. The frequency of A1C testing should depend on the clinical situation, the treatment regimen, and the clinicians judgment. The use of point-of-care A1C testing may provide an opportunity for more timely treatment changes during encounters between patients and providers. Patients with type 2 diabetes with stable glycemia well within target may do well with A1C testing only twice per year. A1C Limitations The A1C test is an indirect measure of average glycemia and, as such, is subject to limitations. As with any laboratory test, there is variability in the measurement of A1C. Although such variability is less on an intraindividual basis than that of blood glucose measurements, clinicians should exercise judgment when using A1C as the sole basis for assessing glycemic control, particularly if the result is close to the threshold that might prompt a change in medication therapy. Conditions that affect red blood cell turnover (hemolytic and other anemias, glucose-6-phosphate dehydrogenase deficiency, recent blood transfusion, use of drugs that stimulate erythropoesis, end-stage kidney disease, and pregnancy) may result in discrepancies between the A1C result and the patients true mean glycemia. Hemoglobin variants must be considered, particularly when the A1C result does not correlate with the patients SMBG levels. Though some variability in the relationship between average glucose levels and A1C exists among different individuals, generally the association between mean glucose and A1C within an individual correlates over time ( 5 ). A1C does not provide a measure of glycemic variability or hypoglycemia. For patients prone to glycemic variability, especially patients with type 1 diabetes or type 2 diabetes with severe insulin deficiency, glycemic control is best evaluated by the combination of results from SMBG or CGM and A1C. A1C may also inform the accuracy of the patients meter (or the patients reported SMBG results) and the adequacy of the SMBG testing schedule. Correlation Between SMBG and A1C Table 6.1 shows the correlation between A1C levels and mean glucose levels based on the international A1C-Derived Average Glucose (ADAG) study, which assessed the correlation between A1C and frequent SMBG and CGM in 507 adults (83 non-Hispanic whites) with type 1, type 2, and no diabetes ( 6 ), and an empirical study of the average blood glucose levels at premeal, postmeal, and bedtime associated with specified A1C levels using data from the ADAG trial ( 7 ).
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