2013 update on the worldwide standardization of the hemoglobin A₁c measurement.

Hemoglobin A1c (HbA1c) reflects a time averaged blood glucose during the previous 2–3 months, and is used as the gold standard for long-term follow-up of glycemic control. The same HbA1c method was used both in the DCCT study published in 1993 (1) and the UKPDS study published in 1998 (2). Following the development of a true reference method by IFCC (3), it was stated in an international consensus that this reference method should be used by all manufacturers for the calibration methods used in the clinical laboratory (4). A second consensus meeting was held in 2009, where the main issue was how the results should be presented to clinicians and patients, and how they should be reported in scientific journals (5). In short, three conclusions were reached at this meeting: