The Role and Quality of Hb A1c: A Continuing Evolution

Since glycohemoglobin was first described in the red cells of diabetes patients in 1968 (1), the test has evolved to become an essential tool for prognosis, monitoring, treatment, and diagnosis of diabetes mellitus. An increasing clinical focus together with the development of diabetes management guidelines based on glycated hemoglobin (Hb A1c)2 necessitated a standardization of the method initially achieved in schemes such as the National Glycohemoglobin Standardization Program (NGSP) (2) and later refined by the IFCC (3).Now that we know the reference values we should be aiming for, the IFCC task force has investigated approaches for setting the analytical quality targets for Hb A1c (4) so that we can know how close to those reference values we need to be; the task force's report is published in this issue of Clinical Chemistry (4). The task force has acknowledged the importance of the Stockholm hierarchy, in which clinical outcome studies are the preferred method of defining analytical quality (5). In Milan during November 2014, the European Federation of Laboratory Medicine revisited the Stockholm consensus and retained clinical decision making at the forefront of the rationales for defining analytical quality, ahead of biological variation and state-of-the-art approaches (6).Hb A1c is ideally placed for using clinical rationales to define quality specification, because we know so much about diabetes outcomes in relation to Hb A1c, and we correspondingly have agreed-on clinical protocols to manage diabetes. The IFCC task force authors have borrowed the excellent example of the …