Toward a Global Overview of HbA1c Test Performance

Abstract

Hemoglobin A1c (HbA1c)2 measurement has been a standard of care for patients with either type 1 or type 2 diabetes for nearly 4 decades. Studies such as the Diabetes Control and Complications trial in type 1 diabetes and the United Kingdom Prospective Diabetes Study in type 2 diabetes in the 1990s have shown how hyperglycemia, as assessed by HbA1c, is associated with the long-term risk of the micro- and macrovascular complications of the disease and the likelihood of having a severe hypoglycemic episode (1, 2). The analytical performance specification (APS) required of a particular test—defining how accurate and/or precise the measurement should be for clinical purposes—is preferably based on data from outcome studies. However, it is uncommon for this information to exist for many routinely requested tests; therefore, less ideal alternatives, such as using biological variation or state-of-the-art technique for the measurement, are often used to derive the APS instead (3). With studies such as the Diabetes Control and Complications trial and United Kingdom Prospective Diabetes trial, HbA1c is one of the few examples in which trial data can directly inform the APS. The IFCC has developed 2 models of quality (i.e., APS) targets for HbA1c, one based on biological variation and the other on clinical outcomes (4). For the latter, a total allowable …